I've just put on 1.25" and I think I could've gone for 1.5", may be because I am running stock tire. With your 285/70, you are probably fine with 1.25. I would say why not 1.5", eh?
I've got 285's with Spidertrax 1.25" and they look awesome! I'm not sure how much of a difference you'll notice with an extra .25". All pro are a little cheaper but sometimes you can find a set of blemished Spidertrax for a good price.