John nailed the single most notable factor, that being, bullet construction.
The deer that I shot this year with Hornady's SuperFormance SST ammunition dropped literally without a step, that from a .308 Win with 150 grain SST, and from a .270 Win with a 130 grain SST. Both deer were shot at just over 200 yards. There was no exit wound on either. In both cases, not only was a follow-up shot not needed, they dropped so fast it wasn't possible. Autopsy of both deer revealed about a 0.5" entrance wound, and minimal meat damage. On both deer, the near-side lung and the heart were literally "liquified". I mean, liquid! There may have been 1, 1" chunk. I mean, liquid. The far side-lung was 100% in-tact, on both deer.
Both of these deer dropped faster than any other game animal that I have shot at similar distances (deer, hog, ram) shot by any of my other firearms cartridges, including 6mm Rem, .257 Wea Mag, .300 Win Mag, .300 Wea Mag, even the .375 H&H, .444 Marlin and .45-70 Gov't. For my purposes, the .308 and the .30-06 are now officially co-equals, thanks to Hornady's SST and GMX offerings. Select the proper projectile, and you're good with either. Use an SST for an immediate "one-'shock'-kill", use a GMX for complete penetration regardless of angle or distance to the target (within reason).
The only other considerations that I might take into account regarding the two, already has been mentioned as being short-action versus long-action, and a 22" barrel versus a 24" barrel. Here too, Hornady's SuperFormance powder has made the barrel length a very nearly mute point. A 130 grain .270 Win SST fired through a 22" barrel has no significant loss of velocity over the same fired through a 24" barrel. Hornady truly has pulled-off a cartridge coup d'état.
I too will echo the fact that I cannot locate .308 Win any where locally. It is dry. Then, I saw this event coming about 3 to 4 years back, and did my due diligence, and made sacrifices in other purchases to afford to stock-up on factory loaded .308 Win, and all other cartridges I own, as well as all of the needed reloading components for each.
Don't get me wrong about the .30-06 Sprg. I wax-romantic for that dear old cartridge, and always will. A few years back I purchased a NIB Model 70 Super Grade. The first was defective. Its replacement was destroyed by a gunsmith about 6 months later. I finally had no option other than a Super Grade on the shelf in .270 Win. I wax pretty romantic for that too what with her having been my first true-love, but she just isn't the .30-06 Sprg. For the pure romance of that ol' .30-06 Srng being cartridge carried into WWI and WWII battles, I would opt for that cartridge. To me, the .30-06 is both Prom Queen and Tom Boy. She'll never disappoint...ever. Is a .30-06 necessary? I can't say it is.
Going back to short-actions and long action, 22" and 24" barrels, Winchester has your back with the "Extreme Weather". I also lust over the Model 70 Coyote Light. But, that doesn't mean I'll break-up anytime soon with my two favorite "girlfriends", my Model 70 Stealth .308, and my Super Grade .270. Choose your poison. Oh, and yes, cartridges that are readily available here today, included the .243, .25-06, .270, the .30-06, 7mm Mag and .300 Mag. Dang .308 is dried-up. Got me a whole military can full-up of Hornady SuperFormance .308 WIn 150 SSTs, and a whole military can, full-up of Hornady SuperFormance, .270 Win, 130 grain SSTs. Can't let my dates go hungry. 8^) Think about it, they can't "reciprocate" if they don't get fed.
Alas, I drift. Happy and safe shooting. By the way, this is one of the best threads that I have ever read at THR! Great thoughts and input fellas! No fan-boyisms, just good reflection and self-controlled discussion. Dang, I have missed THR these past 9 months away.
Geno