I have a pair of these to school in. Very easy to wash, just put them in the washer (although they wash better, like polos, on "cold") and then the dryer and they're as good as new. Actually I have two pair, one with fleece and one without, and I like them both equally so -shrug- just a personal opinion I guess.
As far as open fronts go, they're more popular with Show Jumping riders for several reasons. As far as I know they're the only type of boot used in Equitation (others are allowed I think, but if you did I would not be surprised if you were marked down for not having "conservative" attire) and at rated shows many Eq horses cross over into the Jumper ring and they mostly just keep the same boots on. Since most everyone else is wearing them that's what most people expect, and at bigger shows you look a bit ridiculous in anything else. Not to mention its what you see used in Grand Prix, so its a lot of "monkey see monkey do"
Honestly, while I would school in SMBs or use them XC (if I did XC :P), I wouldn't wear them in the jumper ring. Open fronts look a lot nicer in my opinion. Just my 2 cents