USGames in general is the best, Llewelyn and Lo Scarabeo - though the latter is better, both have way too many warping issues for me, and the cards tend to be thinner - though I did just get the Buddha Tarot published by Llewellyn and the cardstock is excellent (I wonder if the artists have anything to do with that?)
The smaller size Enchanted Tarot is the worst when it comes to thin flimsy card stock, but then I have another deck from St Martins Press that has thicker sturdy cards - so some companies differ from deck to deck. Also, there are other publishers whose cardstock I like, but since I may only have one deck from them, I will stick to the publishers I have more experience with.
I will add that most of my warped decks have been Llewellyn...just had a string of really bad luck with decks from them. Lo Scarabeo, I must say, I have had ONE warped deck from them - so it is unfair for me to include them in my above statement.