pull up belts are where the adjusters on the hips pull up to tighten. pull downs are the opposite. The adjuster is flipped in relation to the belt.
The benefit to the pull-up is that it's easier to tighten by yourself, especially in a seat that fits snug on the sides. I can barely cram my fat arse into the seat and have pull-down adjusters. I can't tighten them by myself, so I have to set them before I sit down, then stretch and pull to buckle it when I get in.
With the pull-up, I could just give them a good yank.
The issue I see is that the pull-up ones are 'only' SFI rated and expire in 3 years, while the pull-down ones are SFI+FIA and expire in 5 years. Same belt material, same adjuster, jsut a different direction. stoopid if you ask me.
This is a pull down belt:
This is a u-type drag racing belt, but the lap belts are a pull-up type. you can see the difference there at least..