I think another important thing to consider is ammo availability. If you plan to hand load, its not that big of a deal, but if you plan to shoot factory ammo, your selections are limited on all of them, but I would say your best bet for variety would be the 6.5x55, and it probably is the most widely supported (a huge European following).
If you asked me personally, I would favor the 6.5x55, but my criterium is probably different than yours.
MEL
If you asked me personally, I would favor the 6.5x55, but my criterium is probably different than yours.
MEL