I don't look at EF-S lenses because I keep a non-EF-S body in the arsenal.
I chose the 24-105mm over the 24-70mm for two reasons:
1. Image Stabilization: I don't care what people say - it is a very useful tool! In this focal range there is nothing I shoot that requires a wide aperture so IS was a big factor in my decision.
2. Weight and focal length: Yeah, I put these two together. I'm mobile, and this lens goes with me everywhere. Less weight and more zoom - speaks for itself!
Would I like to have a 24-70mm in my arsenal, sure! Is it on any of my wishlists? - no. Since I picked up the 24-105mm there are more lenses I'd prefer to have before buying a 24-70mm.
I will say that it was quite a debate choosing between those two lenses though. I completely understand why so many threads pop up about this debate.