Trying to decide on a long lens

[mikew_RIP]

I dont think you will go far wrong with any of the lenses you mention,my word of warning would be about the new 100-400 not having a tripod mount,that is only a problem though depending on how you want to carry it,as far as i can see you would be limited to the camera strap around your neck.

 

[Bukitimah]

What are you shooting, how are you going to use it...tripod, hand held, monopod, subject, distance,lighting conditions, too many variables to recommend any lens. If it is for a specific subject you know how it will mount but if general purpose, I suggest the smallest.....the larger heavier lenses just get taken out less so miss the chance shots. As I said,too many variables unknown.
Do you have shots you could post that show your typical subject and distance?

I think I can agree with you. big lens are great but unless hou are on a specific outing and all geared up, chances re you won't be bringing along the big lens most times. however, without the proper tools, it is also sometimes impossible to shoot the shot you want.