I could be happy with any cartridge from .243 Win all the way to 30-06, if used only for deer and no other game taken into consideration. I qualify this remark by using sectional density bullets at or very near .250 in the smaller bores up to 30 cal. None would be magnums as it isn't necessary for deer only. I'd be more concerned with the rifles one was chambered in. Let me pick the rifle for the game and I'll let you pick the caliber and cartridge, and I'd be just as happy as if I'd picked the entire for myself. The rifles balance, handling and accuracy are more important to me than the caliber. I like to use bigger bores and light magnum rifles when hunting deer in big bear territory in case I unluckily encounter one. I especially then want my pick for rifle above cartridge. The .270 Win is still a fine round for almost all game in continental US, or any other clones from its parent case, the venerable 30-06. No argument from me. I could easily use a 7x57 or any of its clones. I could use a .308 Win and all of its clones. I'd have no problem with other rimmed rounds, if hunting wooded areas and shots limited to 200 yds. I personally use a .243 Win using only 100+ gr bullets for deer in areas with no large brown bear. I own and have used 6mm Rem, 257 Roberts, .250 Savage, 25-06, 6.5x55 Swede, .270 Win, .280 Rem (my favorite all around rifle), 30-06, 300 Win mag, 30-30, 8x57, 338 Fed, .358 Win, 35 Whelen, .35 Rem, .338 Win Mag, 9.3x62, .375 H&H, and even .416 Rem Mag. None of the mags killed deer any better than a comparable rimless round. I don't think there really is just one cartridge that is the best deer round. There are too many good ones that any comparison would be a matter of personal preference.