70-300L or 100-400L

[rcarca]

I shoot with both a 7D and a 5DMkiii. I currently have a 70-300mm f4.5 - 5.6 DO IS USM, and am wondering if I should upgrade it to a 70-300mm f4.0 - 5.6 L IS USM or the 100 - 400mm. I have found the current lens a little soft on both bodies, certainly when compared to my 24-105L and even my 15-85 EFS.

The 100-400 has the attraction of an extra 100mm, but then it is a much older lens. My main use for this historically has been bird photography, and therefore it is better on the 7D. Can anyone comment?

Thanks

Richard

 

[Loswr]

If you don't really need the extra 100mm, the 70-300mm L is the better lens. If you do need the extra reach, the 100-400mm is the way to go. For birds, you almost always need the reach. I'd go with the 100-400mm.

Most (but not all) of my shots in my Flickr Birds and Wildlife sets are with the 7D and 100-400mm (you'll see a couple with the 7D and 70-300 DO in there, too).