I recently upgraded from the 7D to 6D, and am looking to get some length back in my lenses. I had been using a 70-200mm f/4 IS, and liked the length at 200, so around 320mm on FF.
I will be renting for this go around, and then probably purchasing something in this range.
My thoughts are one of the below options:
Rent a 1.4x TC for my 70-200 f/4. This will give me a 280mm lens at f/5.6, based on ISO 12233 crops, it still looks pretty sharp, but autofocus may be iffy.
Rent a 300mm f/4 IS. Less versatility but a stop faster, and sharper.
Rent the 70-300L, good zoom range, sharp, but f/5.6 at 300mm.
Rent a 100-400mm, same speed as the 70-300mm, but the IS likely isn't as good.
If you've had a chance to use any of these options I'd greatly appreciate your feedback!