I know a lot of folks say it’s not necessary but I scratched the hell out of my first two AWs. So much so that it was cheaper to replace the watch than repair it. Life of a plumber, I guess. Don’t really care for the big, bulky snap on ones. Have tried a lot of the little glass ones you put over the screen, they’re nice but hell it takes me 10 minutes to input the code to open the thing in the morning. Scrolling through the apps is a nightmare.
You aren’t going to scratch the ultra. There isn’t much out there that will scratch the sapphire crystal.