Okie, you can go with a 14' foot stock, I had one. All horses liked it, very rarely will you get one that refuses to load in a stock. A 2 horse straight haul is preferred by some owners, however I find horses generally don't like them or require more time training to load.
I just got a trailer, 2 horse straight load. It's just over 12' long. Each stall is 7' x 3' with an open front for the horse to hang it's head over (no tack room, wall or mangers) 2 full size escape doors on either side. It's OPEN inside, feels very roomy. I was always worried about getting a 2 horse straight and it being long enough because my big boy is long. But this one fits great. I spose it depends on the kind of straight you find :)
Over this side of the world slant loads are only just becoming readily available. I have only ever hauled with a 2 horse straight load and find the biggest issue is generally the height more than anything else. A lot of them tend to be aimed at horses under 16hands!
Single trailers I avoid like the plague though. A lot of the horror stories I have heard have involved single straight loads. Posted via Mobile Device
Straight loads are fine, get used all over the country,
Now to the one horse. On the surface it seems ok as you only are hauling one horse, They would make sense IF and a Big IF, they were half the weight, half the cost, and half as hard to tow. But they are not. So there really isnt any advantage to them. They are a bit lighter but most of the weight is in the frame, they are pretty rare and they cost the same or more than finding a two horse. Also on resell. A good shape 2 horse bumper pull will resell quick. One horse ? Not so much. If you have a smaller tow vehicle where every pound counts, maybe they would make sense. I am just not seeing alot of advantages to a one horse.