If you want to have the best of both worlds you can do what I did...get them powder coated and then spray it with bed liner on top of that for some overkill :behindsofa:
I'm not really good at painting/prepping but still wanted something durable that I can easily touch up down the road, so what I ended up doing is having Bud power coat it in textured black (so that there's some "roughness" for the spray paint to bite into); then I sprayed on a few coats of the bedliner that [MENTION=74569]SOcalTRAIL[/MENTION] used.
This way the prep work is all done for me so I don't have to worry about paint adhesion problems, and I can easily patch up any rust/scrapes without having to take the sliders off.
Line-X is really cool and all, but I've gotten some pretty steep quotes in my neck of the woods that steered me away from that option (ranging from $400-$500); not to mention most of these guys told me they can't honor the lifetime warranty since it's not sprayed in the bed of a truck.
Of course, your mileage may vary, but if you did want to go this route I urge you to look into it first and see what your local Line-X guys say, just so there's no surprises later.