Gotcha. I'd just call them and ask if they recommend one brand over the other, but just make certain you get polished stainless steel. I'm big on the image of the trucks and the cleaner they look the better. Diamond just looks bad after a while and even when you wash it, it still doesn't look clean but rather dull instead.
I've had some crappy fenders in the past and I really like the ones I got from them for this new truck. I won't, but I bet that I could stand on them. Sturdy and heavy gauge too.