I am also someone who have been using GPS watches for a decade and half now, starting from Garmin Forerunner 110 in 2011 and having Vertical 2 as my latest watch.
I run in Pacific Northwest on mountain trails that are often under a very dense tree cover, under tall coniferous trees such as Dogras Fir, Red Cedar, Western Hemlock, etc. This is an extremely difficult environment for GPS and historically most GPS watches were very inaccurate.
For a long time I thought that Suunto Ambit 3 Peak with its massive GPS antenna was perhaps one of the most accurate watches, but the new generation of watches with dual-band GNSS that have been released in the last few years, starting with Garmin Fenix 7 are amazingly accurate in this environment compared to anything we had before.
The last generation of Suunto watches with dual-band GPS - Vertical, Race, Race S, Race 2, Vertical 2 - are all very accurate and some of the best in class in terms of GPS accuracy. But in my opinion, still nothing beats the Airoha GNSS chipset that was used in Garming Fenix 7, Forerunner 255, 955, and few other watches a few years ago. I think more recent GPS watches are a bit less accurate even though they may offer better battery efficiency.
Here is a comparison of Fenix 7X Sapphire vs. Suunto Race S - on a similar terrain with the same map zoom level. Both of these are are examples of running downhill on a narrow singletrack trail. Both of these show 6 laps on the same loop. You can see that the track produced by Airoha GNSS definitely looks tighter with tracks from laps closer on top of each other.
[image: 1776988567192-screenshot-2026-04-23-at-4.55.25-pm.png]
[image: 1776987438944-screenshot-2026-04-23-at-4.18.40-pm.png]
To be fair, more recent Garmin watches (Fenix 8, Enduro 3) are definitely less accurate than both Suunto watches and earlier Garmin watches.
Also, distance wise I think Suunto is a bit more accurate. Garmin had a tendency to shorten the distance by 1-1.5% compared to the distance of the GPS track.
