I went thru this dilemma sometime ago, but both here's my 2 cents:
24-70 scores on the aperture (f2.8 is quite helpful) and it is probably superior albeit slightly on the IQ part.
However, personally after a tough time thinking, I chose the 24-105 for the following reasons;
1. it's lighter weight (24-70 is almost 50% heavier)
2. extra focal length from 70-105mm which adds to its versatility as a true general purpose/ travel lens. (I hv gone for some trips with only this lens and I didnt miss much)
3. IS feature, which is very useful when it gets darker especially & u can practically reduce the shutter speed to only about 1/6 or so for handheld shots. In rare cases, it also helps when u want somebody else (w not so stable hands) to take a snap of urs.
When all this comes at a lower price, I went for the 24-105L. The 1-stop aperture loss is ok as u can bump up the ISO by 1 stop and these days cameras have excellent noise control unlike a few years ago.
The choice is urs!