6.5 vs .30cal: everything is a trade-off in some way. If you want a lightweight rifle, recoil is going to be greater with a 30cal. If you want flatter trajectory and less windage with lower recoil, 6.5 will be give the necessary BC with less bullet weight (and therefore less recoil). If energy at great distance is an absolute requirement, then a heavy (210 grain or more) 30 cal bullet launched at 3000+ fps will out-smack the heavy 6.5s at equal velocity. In rifles of equal weight the 30 will pound the snot out of you compared to the 6.5, unless mitigated by an ear-splitting, sinus cavity collapsing brake. For high volume shooting (practice is supposed to be FUN!) a big 30 will need to be fairly heavy, but then it won't be much fun to carry up the mountain to hunt the high country, and ammo will cost more because you use more of everything. Opinions vary about how much energy on impact it takes to kill various critters, and bullet placement will is always important because it doesn't matter how much energy you miss with, only how much you dump into the target. A 300 ultramag with a 210+ grain bullet will hit much harder at 1000 yards than a 6.5 Creedmoor with a 140 grain bullet, but how much practice are you going to enjoy with the "loudenboomer" to be confident or making the shot 9 times out of 10, cold-bore, halfway back of beyond...
Now, for the OP especially: decide how much energy you need at the target, how much recoil you can take repeatedly, and how much money you can spend on ammo, then choose accordingly. But above all, you must like shooting your final choice, or you won't do it enough to be proficient with it.