in six page of replies has anyone asked the OP what he shoots??
Budget is a consideration, but what do you shoot the most?
I think a lot of shooters have owned either the 17-40 or the 16-35, but not both... so there is some bias in those recommendations
I shoot mostly weddings, but some other portraits and events, etc. I've had the 16-35mm v2 on my 5D (2 and 3) for a long time, and shoot mostly weddings. Most of my all time fave images were at the 16 end of that lens! see http://www.brianpowell.info
There is a difference from 16-17mm, and it is noticeable. Also, if you want to shoot under f5.6 or so, your IQ will in fact be better on the 16-35. I love it and shoot all over the range, depending on the ambient light. It's a perfect length for weddings because 16 is dramatically wide on a FF (pulling in sky on outdoor shots) and at 35mm I can take full length portraits or group shots. For journalistic coverage (dance floor, prep shots, etc.) I'm usually pretty wide. It's on the remote camera in the balcony for the ceremony. It does it all! When I travel, it's my landscape lens.
I've owned the 24-105 f4, and the new 24mm TS-E for a while. The only other wide angle I'd want, and it's on my wish list, is the 14mm rectilinear
So what do you shoot?