A buddy and I did a photo trip to the southwest earlier this year (Monument Valley, slot canyons, Santa Fe, etc.). We both used 5D Mark III bodies and shot close to 1000 frames each. I used the 24-70 II, and he used the 24-105. Both produced stunning results. The bottom line is that that 24-105 is nice for having some extra reach, and the 24-70 is slightly faster (f/2.8 vs f/4). And of course the 24-105 saves you a lot of $$$. Either way you can't go wrong. If really torn, rent them both to help you decide. Good luck & enjoy!!!!