Definitely LESS distracting.
Innumerable times I've left my phone in my pocket while driving, and it vibrates. When it KEEPS vibrating I know I have a phone call - so when I get a chance in the next few minutes, either at a light, or while driving when nobody is around, I try to get my phone out by lifting my butt up out of my seat to make my pocket parallel to my legs, then pull it out. This is dangerous. I do it only for phone calls, say I'm on an expressway and the next exit is 20 miles away. I do this, because when I get a call, half the time it's very important.....
Anyways, I do this to check WHO the message is from... if it's important, I'll pull over and take the call....
Well, with a watch I can easily glance WHO is calling, so all this messing around with taking the phone out is gone. And it's much safer.
Glancing at a watch is no more dangerous than glancing at the rear view mirror, fuel gauge, gas gauge, etc. Actually DOING something is a different matter.