I have had straight loads with /without ramps. I have a stock and a 3h Slant now. My horses have been hauled in all without any issues...They prefer the stock I think because they see more..I perfer the stock over anything...More air flow and they usually ride facing the back...I like the slant also because they seem to haul better since they can lean against the partitions and balance themselves better....
My horses and I like the straight load. I prefer a ramp, especially with a slant load. It gives the horses a little more room to back out on, but you do have to be more careful that they don't go off the edge, but probably no more than a step up. Another reason, I like the ramp is because I have a rear tack and I stand on the ramp to get my tack out and can stand on it to get the saddle on. I'm 5'2" and would have a difficult time getting a saddle off the top rack if I had to stand on the ground.
Slant. Ourtrailer would be a four-horse straight load (Two in front, two in back) But we can make it a three horse slant as well if we move the dividers (They swivel so we can just shift them over and it makes invidual slant slots) I prefer step-up as well.
I have a Bison-three horse slant load. It is an older model. Good trailer. I have used all type of trailers. In the end it comes down to the horse. I usually trailer mine alone. The horse is 15 hand, 12 year quarter horse gleding. No big issues. When my horse is alone there is enought room for him to turn around an come out of the trailer head first. I usually discourgage this. We usually have a discussion. He present his points; he is 1,200 pounds, has for legs and really does not want to back out into what he cannot see. I counter that I have more intelligence (will sometimes), I have had to put down horses (tearfully and unfortunately) and unless he wants to walk his fanny back some 25 miles to the barn he will do things my way. Sometimes this actually works.
I have never tried a reverse load, they seem to be popular with the barrel racers here in Texas. I have used a cattle trailer of some sort most my life but recently aquired a Logan 3 horse slant. My horses started hesitating getting in. I took the dividers out and now they hop in again.
I never had a ramp trailer but assisted a few folks with loading their horses into one at shows. They all had ramps. I don't think horses like them if not trained to use one.
I have used a stock box or cattle racks and had horses jump flat footed into one to load up or out, never had a problem whether it be the first time ever or the 100th.
For most horses a slant step up. I have a 2h slant step up, and a 2h straight step up- 1964, I am trying to sell it. I just got the 2h slant and LOVE it - only $2000.. Horse safe, just needs to be sandblasted in a few areas