This is more like the one I use: Farnam SuperMask II Shimmer Fly Mask - Statelinetack.com
I like it because it has a double velcro closure so other horses can't pull it off.
I've never tried one with ears, so I don't have an opinion on that. I think I would like it because the flies bite my horse's ears so bad. But maybe not if other horses try to pull it off that way. Plus they look kinda silly.
Like some others said, make sure you get it on tight enough that flies can't get in (& it's not sagging below their chin to get caught on things) but not so tight it rubs when your horse moves or eats. You will definitely feel like a mean horse mom if you cause your horse to get a sore on her jaw (not that I
ever did that!) Definitely check it every day or better yet, take it off every night.
Yes, I believe there is reduced visisbility when wearing them while it's raining. Think about looking through a window screen that's been sprayed with water. It kinda drives my girl crazy so I try really hard to make sure she's not wearing it when it rains. I would assume there would be more difficulty seeing through it at night as well.
For me, for my one horse, a fly mask is a MUST. They bother her so badly. My other mare I use one sometimes if they seem to be really bad, but she doesn't really like it, so often she doesn't wear one.