I have found that horses load more safely stepping
up than walking up a ramp. The tend to put their heads down when stepping
up where the opposite is true when they walk up a ramp. Also, I have seen
horses slip or step off the side of the ramp and get hurt. But I suppose
with proper training, either is fine, but I wouldn't go out of my way to buy a
ramp for a trailer; just teach the horse to step up. Much
cheaper!!!