I really think the 24-105 f/4 IS L is an under appreciated and under valued lens. Maybe not in this thread, but overall.

That said, I am likely going the other direction. I bought the 24-105 as part of the kit with my 5DIII. It has been a good lens for 2 years but I picked up the 24-70 II in June and think it is the way I'll go. Three primary differences:
  • f/2.8 aperture. While not posted here, I actually shoot a lot of family indoors. I decided the extra aperture was beneficial both for lower light and thin DoF. I will say, I have been burned using the f/2.8 a few times due to the small DoF. To an extent, for random shots around the house, it seems that it is tough to beat f/4-8 and a flash.
  • Extra sharpness and contrast
  • Faster AF in low light/utilizing the f/2.8 AF points on the 5DIII.


The 24-105 f/4 L is a very good lens, so I can understand those selecting it as their primary general purpose zoom. I still sometimes waver as the 24-105 was really very good. The IS was ok (2-3 stops), not as good as the IS on my old 15-85 (solid 4 stops). I am actually tempted by the new 16-35 f/4 for IS.

I am wondering, do you really find the 24-105 that that much more discrete on a 5DIII than your 24-70? Very good lens, no doubt, but comparing 24-70 I vs 24-105, the 24-70I is 0.1" wider and 0.6" longer. The 24-70II is 0.2" longer and 0.2" wider.

I understand what you mean, but if you want to be discrete, I'd be tempted to go with your 50D or maybe another crop camera. I noticed a big difference in how I am perceived as soon as I went to a 5DIII. With my 7D, I think I must have blended in with other photographers with Rebels and xxD camera bodies. But people do notice the 5DIII, with L-bracket, and either the 24-70II or 24-105 mounted on it. I get a lot more random questions about photography now than I used too.