As usual, "more expensive is better" applies here, though as far as I read it not for f8-f11 landscape shots. If you use uwa a lot, the 16-35 might be the better choice, but often it'll be used in a combo with a 24-70 lens - and then it gets more difficult: 16-35+cheap 24-70 or 17-40+expensive 24-70? That's why I've got the 17-40, and at f8 I'm happy so far, it's a good iq (even on crop) and sturdy internal zoom lens.
I use the 17-40 on crop as well, as my general purpose lens. Well built, sealed and performs well, and used on a crop body it's not suffering the same drop off in resolution or vignetting at the corners as it does on a FF body at the wide end, wide open!