In terms of software experience, there are visual differences between stock Wear OS and Samsung’s custom Galaxy Watch interface. Although both watches run on Wear OS 3.5, Samsung uses a custom overlay on top of it that still looks like its older smartwatches based on Tizen OS (via Samsung). You will notice fundamental differences in how the app launcher, settings app, quick settings toggles, and app tiles appear. Notably, Google promises three years of software support for the Pixel watch while Samsung offers four years (via Wired).
Under the hood and in terms of the experience, however, things aren’t starkly different. You can download and run the same variety of apps. On these smartwatches, you can access apps such as Strava, Adidas Running, Nike Run Club, My Fitness Pal, etc. As mentioned above, you can also get exclusive subscription services with both varieties of smartwatches.
In terms of performance, the Pixel Watch uses a Samsung Exynos 9110 processor and an M33 co-processor (via Google). The 11nm chipset is four years old and was first deployed on the Galaxy Watch Active2 in 2019. In contrast, the Galaxy Watch 5 uses a much more advanced and efficient Exynos W920 processor fabricated with a 5nm process.
However, the Pixel Watch makes up for its shortcoming in processing power through a larger 32GB storage and 2GB of RAM compared to 16GB and 1.5GB on Galaxy Watch 5 models.