exxxviii wrote:
It is kind of an un-answer, but my recommendation is "none." In my lifetime of wearing watches, I think I only ever scratched a screen once. All of my watches now look great, and I do not do anything special to be careful with them. I have never damaged an Apple Watch screen in 4 years of everyday wear, and if any screen is exposed, that one is. My Garmin 305XT, 910XT, 735XT were all retired with screens in great shape.
My experience is that the screen on the 735xt is pretty fragile. I have't ever scratched it, but I bumped it against a granite counter top and cracked the screen. Probably would have just lived with it if it was a normal watch, but since I swim with it, I had to replace it.
Since then I've always had a screen protector on it. You pretty much can't tell it's on there. I've broken several protectors over the years, but haven't ever damaged the watch after that first time.