I let the cuff come over the watch, because that is natural and not contrived. Some of my shirts have very small cuffs, in which case the cuff cannot come over the watch, but that is not the same as constantly having to make sure that your watch is visible by hooking the cuff under the watch.
People will catch sight of your watch every now and then. Just make a point of checking the time often.
Yep, I ended up seeing somewhere else that the cuff should come over the watch. But like you mentioned some shirts have really tight cuffs (I happen to like the look of such shirts a lot) and I couldn't get the watch under the cuff if I tried. In such cases it's ok to have it out and on display?