I have a few Ti watches. One, a The Citizen Chronomaster, has been my most worn watch by a long shot this past year. Not a scratch on it due to the Duratect treatment used on the case and bracelet.
I just got another Ti watch, this time an Oceanus with DLC coating. We’ll see how it holds up, but DLC is pretty tough so I’m not really expecting any issues.
I’ve had a Ti diver for about two years now. That one is not coated or treated to any hardening process. It’s not really scratched more than any of the steel watches I have. Perhaps due to the all brushed finish it’s harder to see them, but I have the exact same model in steel too and they are way more obvious on that than the Ti.
Tl;dr: Ti is fine for watches. The weight advantage more than makes up for any perceived “scratchability,” and getting one that has some sort of hardening treatment will actually make it scratch less than steel.