I just started using easyboot epics. My farrier helped fit them to my horse which was a great help. She had several different sizes to try so I didn't have to do the guess the size game. Like kitten_val I like that they tighten at the top of the hoof instead of above the coronet. When they fit correctly nothing can get down inside the boot. We have been in some very deep sucking mud well above the top of the boot. They stay on well and give good traction. We have also ridden on paved roads and there is no slipping which was one of my concerns.
When I first started using them I was a little paranoid about them coming off. I kept leaning over and checking to be sure they were still there
We've pretty much traveled at all speeds and in lots of different terrains, so far so good
Once you get your measurements, give the folks at Easycare a call. They are very helpful at helping you chose the right boot.
From the easycare web site-
Phone M-F 8-5 MST