Tough choices! I like the first best, because it is xw/xt, but am not a fan of ramps, so I'd want to convert to step up. For the price, I'd plan on getting a brake job right away, too. I like the red one, but again would want a brake job. Also, is that a vertical bar going down center at entry, as opposed to being wide open for loading? The last one is decent, but I'm not a fan of slant load.
I think it depends on what you prefer.... straight/slant, ramp/step up, extra size, etc.
I live in the northern mountains of Utah with my wonderful husband, 5 horses, 4 dogs, 2 cats, 32 geese and 9 ducks. Life is good.