Forerunner 170 vs Coros Pace 4

Spec sheets make this look like a battery contest, and Coros wins that easily. I think the better question is who writes your training. Garmin wants to hand you today's session. Coros gives you the numbers and a plan builder, and leaves more of the thinking to you.

I haven't worn either. Measured results here are the named outlet's, and I checked everything on 3 November 2026.

£259.99 on garmin.com (UK), checked 3 November 2026. £229 on coros.com (UK), checked 3 November 2026.

Plans: who decides today's run

Garmin's press release says Garmin Coach plans adapt daily to health and recovery metrics, with lower-volume run/walk options for newer runners. T3 rates the 170's "excellent training guidance" and its personalised workout suggestions as the reason to buy. Tom's Guide found the quick workouts could set hard sessions that needed scaling back.

Coros lists personalised marathon plans and a builder in its app for making your own. DC Rainmaker built a 400 m repeat session directly on the watch and reports that it worked fine.

There's one open question on the Garmin side. TechRadar's Forerunner 570 review says adaptive training plans moved to the paid Connect+ tier, and I couldn't confirm how that lands on the 170. Check before you buy for the plans alone.

Metrics: what you can read

Garmin lists Training Readiness, Training Status, HRV Status, VO2 Max, running power, race predictor. Coros lists EvoLab: recovery, fatigue, training load, race predictor, VO2 max, threshold zones.

Those lists aren't equivalent, and brands calculate these scores differently. T3 marks the 170 down for having no lactate threshold metric. Coros's threshold zones cover part of that gap, though I read no test of how close they land.

DC Rainmaker has a specific complaint about Coros. The Pace 4 resets its training-load number each Monday morning on the watch, even if you ran a marathon the day before. His point: your body doesn't reset on Mondays. He says the app handles it differently.

Recovery and readiness scores deserve some suspicion on both. Lepley 2026, a peer-reviewed narrative review in Sensors, says there's no gold standard to validate them against, so treat them as prompts. I cover what the VO2 max figure is in what your watch estimates. A watch isn't a medical device, and neither estimate is a lab result.

GPS and heart rate in published tests

For GPS, the Pace 4 has the hardware edge: dual-frequency against none on the 170. T3's reviewer ran it beside a Forerunner 970 and couldn't see much difference, though not in a challenging GPS area. DC Rainmaker calls its tracks very good.

The 170 did better than its hardware suggests. The Run Testers say it matched a Forerunner 970 and a Pace 4 in multi-band mode, with the caveat that they would still want multi-band in cities. These are all independent, non-peer-reviewed tests. I found no peer-reviewed GPS study on either watch, and instant pace has no solid independent figures that I could find.

On wrist heart rate, DC Rainmaker says the vast majority of his Pace 4 workouts were really good. Outdoor rides were the exception, with the sensor struggling at quick stop-starts. The Run Testers found the 170 matched a chest strap. Tom's Guide's reviewer has found its sensor generation a little less accurate than Gen 5.

On intervals, The5krunner measured the 170 in short reps at +0.5 bpm bias, with limits of -7.8 to +8.7 bpm against a Forerunner 970 and HRM 600 strap. DC Rainmaker called one Pace 4 session of 400 m repeats spot-on, with no figure. These are single sessions, independent and non-peer-reviewed. If your plan is built on intervals, wear a strap. My strap pairing guide covers the steps, and Coros lists Bluetooth for the Pace 4's sensors.

Battery in workout mode

Coros's claims: 41 h, All systems (High), then 31 h, All systems, dual-frequency. Garmin's for the 170: 20 h, GPS only. Those modes differ, so the gap is wider than it looks: T3's reviewer estimated 14 h from the 170 on all systems.

For a marathon, 42.2 km (26.2 mi), neither is short. Battery counts on a long block of weekly mileage, or on a slow ultra. The Pace 4 also has a triathlon profile that the 170 lacks.

Pick by how you train

Buy the Pace 4 if you follow your own plan or a coach's, or you might race a triathlon. At £229 against £259.99 on each maker's UK store, it costs less too.

Buy the 170 if you want daily guidance and you own ANT+ sensors. Garmin Pay and Garmin's wider ecosystem count if you already live there.

My Forerunner 70 vs 170 comparison covers the step down from the 170. The marathon goal page lists the rest.