As far as safety goes, horses can find a way
to get hurt no matter which you use.
As far as step height, I've had many that would
happily jump into a pickup stock rack, but hated to walk into a closed trailer
with or without a ramp. Most would turn around and jump down from
the pickup just like cats. One was too big to turn, he just backed
carefully down the sloping tailgate and stepped off.
(Was kind of hard on the tailgate as he usually
wore borium shoes) Never ever had even a scratch on the
horse.
I think some horses dislike the ramps because they
feel movement as they put weight on.
Having used every possible kind of thing to haul
horses, I like the slant load step ups best for many reasons. Most
have been hashed over already.
One item I insist on with any step up is the
addition of a rubber bumper on the edge of the step up.
And I have loaded and unloaded most kinds of
horses, broke and unbroke, most breeds or mixes there
of.
