I would go with a slant load. Personally i hate straight loads. Most horses prefer to stand at an angle in the trailer, not straight on. Unless the straight load is really wide, they don't leave much room for the horse on either side. I also think it is more dangerous for the handler, yes it may have an escape door, but ive seen too many people who hurry out the escape door when the horse gets worried and the horse either tries to back up really quick, and if the door isn't closed can fall out from the back and really freak out. Ive also seen horses try to come out of the escape door and get really stuck. That is very dangerous and horses get seriously injured.
I would suggest getting a slant load. I have a two horse slant load with a nice tack room. The tack room can swing open and the saddle racks and hooks are removable so it would become like a stud stall.
I don't use a ramp because my horse would have a fit and a half trying to convince her that wasn't going to break off under her. I sometimes with i had one for my two year because i think thatd be helpful with her, but ramp or no ramp really depends on the horse. If your horse is fine loading with ramp and likes that better, go with a ramp. If not, no ramp.
I do caution you with getting a trailer that has the ramp as the door. The ramps tend to take a beating going up and down and having the horses walk on them, and if they come lose you can also have a very bad situation if your horses are int he trailer. If you do end up with one that has the ramp with the door, always make sure to use the butt bar, if the horse was able to break their tie and came back out real quickly while you were trying to put the ramp up you could get seriously injured.
Again, i prefer slant load with no ramp...just my personal preference.
Good Luck!