I have a 700 "Classic" in 6.5x55. It is on it's 3rd barrel, so you know it gets shot a lot.
Simply a rifle to love. Very effective in the field as well.
I own a 260 in a 700 BDL. As Doug already stated, any difference between the two is purely academic.
Had a Winchester M70 FW in 6.5x55, but would have had to rebarrel to get it to shoot, so I sold it.
[I don't have a problem with rebarrelling a worn out tube, but a new one should shoot better than 3moa]
I also had a Ruger 77 Mk II 6.5x55 a while ago, and it was very accurate. Got talked out of it by a friend, though.
I would simply choose the rifle I liked best in either chambering.
Regards, Dave.