Polar Vantage M3 vs Forerunner 570

Figure	Vantage M3	Forerunner 570
GPS battery	30 h performance mode, manufacturer claim	18 h GPS only, manufacturer claim
Multi-band battery	Not stated	14 h, manufacturer claim
Weight	53 g with band, manufacturer claim	50 g, 47 mm version, manufacturer claim
External sensors	Bluetooth only, no ANT+, manufacturer claim	ANT+ and Bluetooth, manufacturer claim
Maps	Offline maps, manufacturer claim	None, per TechRadar
Triathlon plans	Not stated	Garmin Coach triathlon plans, per TechRadar
Transition handling	Not stated	Multi-sport tracking, per Women's Running
Training metrics	Training Load Pro, wrist running power, swim metrics, manufacturer claim	Training Readiness, Training Status, VO2 Max, lactate threshold, running power, manufacturer claim

Before comparing anything else, look at your bike. Polar states it plainly: the Vantage M3 doesn't support ANT+ devices. If your power meter or speed sensor only speaks ANT+, that one line may end the argument.

I haven't worn either watch. Tests below belong to the outlets named, and I checked all of this on 3 November 2026.

£279.20 on polar.com (UK), checked 3 November 2026. £429.99 on garmin.com (UK), checked 3 November 2026.

Sensors on the bike

On the 570, Garmin lists ANT+, Bluetooth. On the M3, Polar lists Bluetooth only; no ANT+. It says cycling support covers Bluetooth power meters and speed and cadence sensors.

Check your power meter's spec sheet before you buy. Your chest strap needs the same check. The Polar H10 pairs over Bluetooth, and I compare it with the Garmin and Wahoo straps in my strap comparison.

Plans for a triathlon build

TechRadar says the 570 gets Garmin Coach triathlon plans and multi-sport custom workouts. Women's Running confirms a triathlon profile and multi-sport tracking in one session. TechRadar also warns that adaptive training plans now sit in the paid Connect+ tier. I couldn't confirm which triathlon plans that touches.

Polar's page describes a personalised Running Program for race distances, plus swim metrics such as SWOLF and stroke detection. Polar calls the M3 a multi-sport watch. In the page text I read, I found no description of a triathlon plan or of how it handles transitions, so those rows say "Not stated". TechRadar reports a separate paid Polar Fitness Program with training plans, in a piece about the Polar Loop.

So the 570 has the clearer plan for a triathlon build. Whether the M3's tools are enough depends on whether you already follow a coach's plan. If you do, this section stops mattering.

Battery across a race day

Polar's claim: 30 h, Performance training mode. Garmin's: 18 h, GPS only, then 14 h, All systems plus multi-band. I found no matching dual-frequency figure on Polar's side.

A sprint to a 70.3 fits comfortably on both. A slow Ironman day is where it gets tight on the 570 with multi-band on. T3's reviewer got just over 24 h in GPS mode from the M3, under the claim but still clear of Garmin's GPS-only figure. TechRadar reports about 14 h from the 570 using all-systems GNSS plus music.

GPS and heart rate in tests

Android Central's reviewer ran the M3 against a Fenix 8, a Coros armband and a Polar H10. GPS results were respectable, with distance within the Garmin's margins, though he says many tests were short jogs and long walks. Tree cover produced more wavering.

Heart rate gave him "whiplash". Average heart rate on most runs was about 1 bpm below the reference, a small gap. On walks it sat 5 to 10 bpm off for sustained stretches, and a track run disappointed him. He'd buy an external monitor for anaerobic work. T3 also reports occasional lag in sprints and intervals. Both are independent, non-peer-reviewed tests, and the Android Central one was explicitly incomplete.

TechRadar's reviewer found the 570's Gen 5 sensor kept up well in high-intensity efforts, and its dual-band GPS held in cities and woods. That's one reviewer's impression, with no figures I can quote.

The only peer-reviewed GPS study I read, Gilgen-Ammann 2020 in JMIR mHealth, tested 2019-era watches including older Polar and Garmin models. Tested error ran 3.2% to 6.1%. Neither watch here was in it, so I won't transfer it.

Neither has a measured open-water result that I could read. That's a real gap for a triathlete, and I'd rather say so than guess. If open-water tracking decides your purchase, look for a recent swim test before you pay.

A sports watch isn't a medical device. Its heart-rate and recovery numbers are estimates for training, and a chest strap is the safer choice when the numbers steer hard sessions.

Maps and which to buy

Polar lists offline maps on the M3. TechRadar confirms the 570 has none. If a bike course in unfamiliar country worries you, that counts. For a known loop, it won't.

Buy the 570 if you own ANT+ sensors or want plans built around three sports. Buy the M3 if your sensors are Bluetooth, your race runs long and maps appeal. It's also the lower outlay of these two, at £279.20 against £429.99.

My first triathlon list has other options, and the triathlon goal page sorts them.