I've heard 6.5 CM gives better long range ballistics and less felt recoil than a .308, but a 6.5 typically runs smaller bullets - which means less killing power and less of a "ping" on steel.
I also almost NEVER find 6.5 CM brass on the range - my guess is everyone who shots it reloads it, whereas .308 brass is much more common.
I'd say I find 20-50x as much reloadable .308 brass than I do 6.5cm.
As Canadians, that's a VERY important factor to take into account as well: ammo availability, because it's not uncommon for some calibers of ammunition to be unavailable (or in very low supplies) for years at a time.
That's why a lot of guys reload (myself included) - because we've lived through ammo shortages and it's not fun.
For the better part of the past 15 years it usually happens when an American Democratic is president.