When I was younger I bought over the knee boots. I absolutely loved them and I got a lot of wear out of them. I didn't wear them with very short skirts, I wasn't brave enough.
I wore them with long, medium, to the knee length skirts, all sorts of trousers. While some would say it's a waste wearing OTK boots and covering them up, it wasn't really, I hated tops of boots showing (if wearing calf height boots or ankle boots). I hated sitting down and the whole top of the boot on view, I'd be constantly pulling my skirt down over the tops. I'd end up having to wear tights with them in case my knees/ just below the knees were on show. It's difficult to explain but with OTK boots you just wore socks, pulled on the boots and there was no gaps, no bits of leg showing, no bare knees.
The other reason I liked them was because they were always much comfier and you could get a really good height in heel, they just gave a better look to an outfit instead of a Chelsea boot etc even trousers.
The other thing is they go with many outfits, so you get your monies worth, you're not looking through your wardrobe for footwear to go with the outfit you're wearing.
If you do decide to buy some definitely try them on rather than buy online, all these boots fit differently, some are tight on the knees and some tight on the calves.