I’ve used Cavallo Trek boots and Scoot Boots, and I like both. Cavallos are easy to put on and they don’t have any screws that could come loose. My horse wore Cavallos for 6 years, and they never came off and they never rubbed. Then, last summer, they rubbed blisters on 3 feet after a ride. I examined the boots and couldn’t find anything wrong with them. The only thing I could figure was that I hadn’t been riding enough to keep his heel bulbs tough, and we had a very wet spring and summer which also contributed to soft skin.
After that experience, I decided to try Scoot Boots because they’re open in back and can’t rub the heel bulbs. I find the Scoot Boots are harder to put on, but once they’re on, they’re fine. They’re easier to clean than the Cavallos–just rinse with water. I also like the open design on the Scoots because it’s lighter on the hoof and allows water to drain more easily. They’re like hiking sandals, whereas the Cavallos are hiking shoes.
My horse goes equally well with either boot, meaning he just tanks right down rocky roads at a fast trot without flinching.
My advice is to first measure your horse’s feet (width at the widest part and length from the toe to the heel buttress) and then use the manufacturer’s size charts to see which brands look like they will fit. If more than one brand looks good, then think about what the weak points of a boot might be, such as screws that could come loose, cables that could break, and so on. Like others have said, the best boot for your horse is the one that fits.