My choice of .308 came, not because I figured them to be absolute equals power wise, because they are not. In my opinion there will be 100-200 fps for any given bullet. As I said in my previous post however, most game animals could never tell us the difference!
I chose the .308 because the "big game" im my area are big, northeastern whitetails and black bears, and for those animals I believe the .308 to be completely sufficient. In fact, in the area where I live (my county describes itself with the slogan, "enchanted mountains") with the generally short ranges, the old 30/30 lever is a good choice.
I like the accuracy, and my being 76yrs old..the gentler recoil and shorter bolt stroke and the Ruger American's 6.12 lbs weight is a plus, as is the rotary magazine.
Of course, this wouldn't have come about for me, had I not given my Marlin 336 to my #3 grandson.

I've been passing my guns to my grandkids in recent years...then discovering.."hey I could have still used that"...so I get another.
So, I replaced the Marlin with the Ruger .308 and a CVA Scout in .44 magnum (same grandson has my old H&R .44 mag)..
Judging by results when hit at my usual ranges, I doubt the deer could tell the difference between the .308 & .44 mag either.