IMO, the ramp has better utility in larger (taller) rigs. If you have a 1 man stand, loading in/out of a barn door style is pretty easy, probably easier, in fact, in the case of smaller, shorter rigs like a 5x8. This is chiefly because the shorter height translates to a steeper ramp angle, which makes for a bigger chore floading/unloading. With a barn door style & a 1 man stand, you can roll the front into the trailer as you lower it. Also note that the actual door W < 5’ in a 5x8.
I briefly had a 5x8 ramp, but sold it to the neighbor & upgraded to a 6x12 ramp, & the difference in the ramp utility was nontrivial.
I would assume that if weight is a concern you are looking at aluminum trailers? Just did a quick search the difference in weight between a 5x8 and 6x12 is a little over 300lbs, not really a huge difference. In between is 5x10 and 6x10 as well.
If I was hauling 1 kart I would go with a ramp style and strap the kart down still on the pit cart.
With any single axle trailer the challenge is making sure you tongue weight is ideal, too much and you car is doing wheelies too little and you will have the fish tail of death.
I’m looking for a 5 to 6 foot x 10 box trailer that weighs less than 1000lbs and has a rear door width of greater than 55.5". Also want it to fit in my garage, so it can’t be any more than 79" inches tall. I’m willing to sacrifice having to crouch a bit to pack up the kart. The lower the better for aero and makes it more towable behind a standard car or small SUV.
What I’ve found is I need to go to 6 wide or the rear door is too narrow. Also the weight goes to 1200#.
Weight matters a lot less than drag. 3’ tall x 9’ long x 5’ wide is about ideal. Yes, you will need to be able to tie down the kart in minimal space, but one strap really will hold it if the front wheels are chocked. Toolbox would then go behind the kart, and spares on top.