Which is better for running and race training?

The Galaxy Watch 9. Running Coach gives real-time feedback and built-in plans for 5Ks and marathons, which the Pixel Watch 5 does not match.

Can I swim with either watch?

The Pixel Watch 5 is rated 5 ATM, so it handles pool laps and showers. The Galaxy Watch 9 has no listed swim-depth rating, so keep it out of the water.

Samsung rates the Galaxy Watch 9 at up to 30 hours. Google does not publish a figure for the Pixel Watch 5, so real-world battery life is the open question.

Is the Pixel Watch 5 worth stepping up to?

If you want more storage, water resistance and Gemini health help, yes. If training plans and sleep coaching matter more, the Galaxy Watch 9 gives you more.

Do both work with any phone?

No. Both are Android watches. The Galaxy Watch 9 works best with a Samsung phone, and the Pixel Watch 5 is built around Google services.

Samsung Galaxy Watch 9 vs Google Pixel Watch 5

The Galaxy Watch 9 is the better pick for Android users who want the deepest fitness and sleep coaching, a bigger screen and Samsung's blood pressure cuff integration. The Pixel Watch 5 wins on storage, water resistance and the cleaner Google Health plus Gemini experience. Both are aluminum Wear OS watches with bright 3000-nit screens, so the choice comes down to ecosystem and training depth rather than build quality.

Choose the Galaxy Watch 9 if you train seriously, want Running Coach and Fitness Index programs, and already use a Samsung phone.
Choose the Pixel Watch 5 if you want double the storage, 5 ATM water resistance and Gemini-powered health insights in a lighter Google-first setup.

Prices

Samsung Galaxy Watch 9: $255.00 at eBay (checked today)
Google Pixel Watch 5: $289.00 at eBay (checked today)
Difference: the Samsung Galaxy Watch 9 is $34.00 cheaper than the Google Pixel Watch 5 today