COLMI i28 Ultra vs COLMI M42: Which Premium COLMI Smartwatch Should You Buy?
The COLMI i28 Ultra and the COLMI M42 are the two most premium smartwatches in the COLMI lineup, and choosing between them is the most common dilemma among buyers who've decided to invest in the best the range has to offer. Both are AMOLED watches with magnetic straps. Both deliver comprehensive health monitoring and 100+ sports modes. Both look and feel significantly more expensive than their price tags suggest. So what actually separates them, and which one should you buy?
This is the most direct, detailed comparison of these two watches available — covering every meaningful difference and giving you a clear recommendation based on your priorities.
At a Glance: The Core Differences
| Feature | COLMI i28 Ultra | COLMI M42 |
|---|---|---|
| Display | 1.43-inch AMOLED 466×466px | Slim AMOLED |
| Design philosophy | Premium all-round with colour variety | Maximum elegance and slim profile |
| Colour options | 6 (Rose Gold, Silver, Black + magnetic variants) | Multiple but fewer |
| Strap | Silicone or magnetic (model dependent) | Magnetic standard |
| Battery life | 7–10 days | ~10 days |
| Sports modes | 100+ | 100+ |
| GPS | Phone-connected | Phone-connected |
| Calling | No | No |
| Price | ~£44 | ~£47 |
Design Philosophy: The Fundamental Difference
The i28 Ultra and M42 approach premium smartwatch design from fundamentally different directions, and understanding this difference is the key to making the right choice between them.
COLMI i28 Ultra: Premium Through Variety and Display
The i28 Ultra earns its premium positioning through two things: the breadth of its colour and strap options, and the quality of its AMOLED display. Six variants — Rose Gold, Silver, and Black in both standard silicone and magnetic strap configurations — give it more personalisation options than any other COLMI watch. The 1.43-inch AMOLED at 466×466 pixels is pin-sharp and visually stunning. The magnetic strap variants snap shut with a satisfying click and lie completely flat on the wrist.
The i28 Ultra is the watch for someone who wants a premium wearable with genuine colour and style variety — the ability to choose exactly the right colour combination for their personal aesthetic, and to get an AMOLED display of exceptional resolution at a competitive price.
COLMI M42: Premium Through Refinement and Slimness
The M42 takes a different approach. Rather than competing on colour variety or display resolution, it competes on design sophistication: the slimmest profile in the COLMI lineup, a magnetic strap as standard, and an overall aesthetic that's more analogous to a premium fashion smartwatch than a fitness tracker that also looks good. The M42 looks at home alongside a suit in a way that even the i28 Ultra doesn't quite achieve.
The M42 is the watch for someone who specifically wants the most elegant, professional-looking wearable in the COLMI range — a watch that draws compliments in professional settings and looks appropriate at formal occasions without screaming "tech product."
Display Comparison: Resolution vs Form Factor
i28 Ultra: 1.43 Inches at 466×466
The i28 Ultra's AMOLED display is the most technically impressive screen in the non-GPS COLMI range. At 466×466 pixel resolution with AMOLED technology, text is crisp and sharp, watch faces look stunning, and health data is presented with genuine clarity. The 1.43-inch size gives good readability without making the watch oversized for most wrists.
Watch faces on the i28 Ultra look genuinely premium — the pixel density ensures that even detailed analogue faces with fine lines look sharp rather than pixelated. The AMOLED technology produces deep blacks that make dark watch faces look spectacular, and the colour reproduction is vivid and accurate.
M42: Slim AMOLED, Optimised for Elegance
The M42's AMOLED panel is optimised for its slim form factor rather than maximum resolution. While the display delivers excellent AMOLED quality — true blacks, good colours, responsive touch — it doesn't match the i28 Ultra's pixel density in direct comparison. For most everyday use cases, this difference is not practically significant. Watch faces look good and health data is clearly presented. But if you place the two watches side by side, the i28 Ultra's sharper, more vivid display is noticeable to most eyes.
The M42's display benefit comes from its relationship with the watch's slim form factor: the watch looks more refined overall because the display doesn't dominate the case, creating a more balanced, watch-like aesthetic rather than the "screen on a strap" look of display-first designs.
Display winner: i28 Ultra on raw display quality and resolution. M42 on overall watch aesthetic and form factor elegance.
Form Factor and Wrist Presence
This is the area where the M42 has the most distinctive advantage. The M42 is the slimmest smartwatch in the entire COLMI range. Its case sits low on the wrist and has a profile that's noticeably thinner than the i28 Ultra. This slimness has several practical implications:
- Suit and shirt cuff clearance: The M42 slides under a shirt cuff without resistance in a way the i28 Ultra — slightly thicker — may not always accommodate as cleanly
- Overnight comfort: A slimmer watch is more comfortable to sleep in. The M42's low-profile design creates less wrist awareness during sleep than the i28 Ultra, which matters for consistent overnight health and sleep data collection
- Perceived elegance: Thin watches have historically been associated with luxury and refinement in traditional watchmaking. The M42's slim profile creates an immediate impression of quality and restraint that bulkier smartwatches, regardless of their display quality, cannot replicate
The i28 Ultra is not a thick watch — it's competitive with other premium smartwatches in its price range. But the M42 is genuinely in a different category for slimness, and this distinction matters enormously for the professional and formal-wear use cases where the M42 is the natural recommendation.
Strap Comparison
Both watches offer magnetic strap options, but the M42 makes the magnetic strap standard across all variants. The i28 Ultra offers both silicone strap and magnetic strap configurations depending on the specific colour variant chosen — some i28 Ultra variants use standard silicone straps while the premium magnetic variants are specific colour/strap combinations.
If the magnetic strap is important to you — for the ease of attachment, the flat closure on the wrist, or the aesthetic — the M42 guarantees you get it regardless of which colour configuration you choose. The i28 Ultra requires choosing specifically the magnetic strap variants (Rose Gold + magnetic, Silver + magnetic, Black + magnetic) to get this feature.
Colour Options
The i28 Ultra wins decisively on colour variety with six configurations: Rose Gold (silicone), Silver (silicone), Black (silicone), Rose Gold (magnetic), Silver (magnetic), and Black (magnetic). This range covers the major colour preferences across male and female buyers.
The M42 typically offers fewer colour configurations, and the available options vary by market. For buyers whose colour preference is specifically something the M42 offers, this is not a concern. But for buyers who specifically want the Rose Gold magnetic strap combination — one of the most popular choices across the COLMI range — the i28 Ultra in that configuration is the primary option.
Colour variety winner: i28 Ultra (six options vs fewer M42 configurations).
Health Tracking: Essentially Identical
For most buyers' purposes, the health tracking capability of the i28 Ultra and M42 is functionally identical. Both offer:
- 24/7 continuous heart rate monitoring
- On-demand SpO2 measurement
- Automatic sleep stage tracking (light, deep, REM)
- HRV-based stress monitoring
- Step counting and calorie estimation
- 100+ sports modes
- Sedentary reminders and breathing exercises
- Menstrual cycle tracking via Da Fit app
Neither watch has built-in GPS (for GPS, look at the P82 or V76) and neither supports Bluetooth calling (for calling, look at the P71 or P82). The sensor hardware and health monitoring algorithms are equivalent between the two models.
Health tracking winner: Tie — no meaningful difference for everyday health monitoring purposes.
Battery Life
Both watches deliver approximately 7 to 10 days of battery life under typical conditions. The M42's optimised power management in its slim form factor often produces slightly better battery performance for equivalent usage patterns, putting it toward the upper end of the 7 to 10 day range more consistently than the i28 Ultra. In practice, both will comfortably last a working week for most users.
Battery winner: M42 (marginally, through better power optimisation in its slim form factor).
Price
The i28 Ultra (standard silicone variants) is typically the more affordable option at approximately £42 to £44. The i28 Ultra magnetic strap variants are priced slightly higher. The M42 sits at approximately £47. The price difference between the two is typically in the £3 to £8 range depending on specific configurations compared.
This price difference is small enough that it should not be the deciding factor. The choice between these two watches should be made entirely on design preference and use case rather than price.
Companion App: No Difference
Both watches use the same Da Fit companion app (free, iOS and Android) with no difference in functionality, data access, or subscription requirements. The app experience is identical between the two models.
The Definitive Choice Guide
Choose the COLMI i28 Ultra if:
- You want the sharpest, most vivid AMOLED display in the COLMI range
- Colour variety matters — specifically if you want a colour or strap combination that the M42 doesn't offer (particularly Rose Gold or the six-way personalisation options)
- Display quality is more important to you than slim-profile elegance
- You want to save a few pounds vs the M42 and the slimmer design isn't a priority
- You're buying as a gift and want maximum colour choice to match the recipient's preferences
Choose the COLMI M42 if:
- You work in professional settings where the watch needs to look appropriate alongside formal or business attire
- Slim profile and low wrist presence are priorities — for formal occasions, suit-wearing, or shirt-cuff clearance
- Overnight comfort is important and you want the least obtrusive watch for sleep
- You want a smartwatch that genuinely looks like an elegant fashion item rather than a fitness tracker
- The magnetic strap as a guaranteed feature (not dependent on colour variant selection) is important to you
Our Recommendation
For the majority of buyers choosing between these two models: if you spend significant time in professional settings and want a watch that works as well at a client meeting as it does at the gym, buy the M42. Its slim profile and elegant design do something no other COLMI watch achieves — it genuinely suits formal wear without any visual incongruity.
If professional versatility is less of a priority and you want the best possible display quality with the widest colour choice, buy the i28 Ultra. The 466×466 AMOLED display is exceptional, and six colour/strap configurations give you genuinely more personalisation than almost any other budget smartwatch.
You cannot make a wrong choice between these two watches. Both are outstanding for the price. The decision is a matter of personal taste and lifestyle priority — and both will deliver an experience that regularly surprises people who haven't considered that a £45 to £47 smartwatch can look and perform this well.