If you don't know how to wrap polos properly (which I think everyone should learn how to do) use boots. I've never had a problem with using polos in all the years I've been riding and jumping. The only time they have come off is when my horse actually tears them off his own legs (you know like with his mouth)
I actually find it faster to throw a pair of polos on a horse then a pair of boots. With my boots I always have to readjust them to insure they are on properly whereas rolling polos on my horse is a no brainer I've been doing it for so long.