i've been racking my brain over this. i think i am going to stick w/ the 600mm for now. i can hold it "ok". and i like that extra 100mm, but as much as i change my mind, im sure i'll have a different answer tomorrow.
The other problem I have with the 500 or 600 is they are prime lenses. I have to crop the photo on the fly. The 500mm minimum focus range is 15 feet... When shooting grizz, it is often difficult to get the entire bear in frame (and I cant switch lenses during those situations)! 


