Hands DOWN, go to Clinton Anderson's site and look for his videos on trailer loading. His method is the MOST useful getting a stubborn or scared horse to load in a trailer, by lunging, constantly changing directions, putting the horse between you and the scary thing, then letting them rest ONLY when they approach and/or load.
I hardly ever had trailer-loading problems until a few years back--sold THAT horse, but my 5yo KMHSA was scared of MY trailer. NOW, he loads super easy.
I've been watching his program for a few years now--DON'T agree with 100% BUT, THIS does work bc it's a positive release after pressure. Here's the start thru finish with one problem horse~
IF you go to his site, he does sell DVD's to help. If your horse panics bc he's afraid of the trailer and hurts YOU, your hospital bill will be a lot higher than the cost of a DVD--just sayin'. DH and I are convinced that this works. It was difficult for us bc our older herd loaded/unloaded without any problems, so this was NEW to us. Watch and I think you'll be able to do it. =D