Between the adorama and arista: I have used both pretty extensivley (have a lot of the adorama at home, all arista at school) and find the adorama to be nicer. I think it's about the same price too. If it's proof sheets only, it really doesnt matter though, so i'd just get whatever's cheaper. for proofs i use a kodak grade 2 drug store level paper, with the name of the paper printed on the back and all. really crappy paper, but i got a partially used 500 box for free, so i just use it for proofs, it is great for that purpose.
-Austin