The 243 with a 95 Berger is plenty bullet for any deer in America out to 350 yds (even further) providing you're only taking mostly or fully broadside shots. I wouldnt try a "Texas Heart Shot" or sharply quartering away at 350 with one however.
Your answer really depends on how you hunt and what you want to use. Which gun are you most confident with? Which one do you have the most trigger time with? Which one do you have the most ammo for? Which one do you enjoy shooting the most?
If there's LR running shot possibilities, or if you don't usually have or take the time to wait for standing broadside shots, or if you're likely to only get a brief glimpse of the deer before the shot and can't afford to be picky about body position of the deer, I'd say use the 308. If you sit and wait overlooking openings or fields or can realistically expect broadside shots, then the 243 is plenty and then some.
Cant comment on the effectiveness of the 308/175 SMK. Unfortunately I've got no experience with that bullet.
I did however see a friend of mine make a LR shot with a 300 grn 338 version on an antelope and the lope never knew what hit him. Fell over dead instantly. Sharply quartering toward body position but bedded. Bullet went in in front of the shoulder and didn't come out. Thinking it was around 700 yds, but don't remember for sure.
Maybe someone else that's got experience with the 308/SMK on game can give some insight.?
I'm kinda in the .243 Win corner on this one.. If I had the time I think I'd run a Berger 87gr VLD in it. I have a friend that shot a nice buck this year using this combo, it was devastating good. In fact I'm witching my 6XC deer rifle to the Berger 87gr VLD's
Obviously were talking about something the .308 Win would have no problem doing as well.
Weekend is over and the 175 SMKs worked just fine. My son made a less than perfect shot on this buck. 50 yard shot in the gut. Didn't matter though the SMK made soup of his inards and exited with a golf ball size hole.
Got try out the 95gr bergers out my 243 this morning. The fox was DRT but the buck took a 80 yard shot just behind the shoulder slightly high. He ran about 100 yards and piled up. It took a while to find him because of no blood trail. The bullet did not exit but destroyed his lungs.
I am kinda suprised that bullet didn't exit. My son's 243 has been shooting 85 grn Barnes on big muleys and some whitetail for quite a few years now, they almost always pass completely through on a broadside lung/heart shot.
Curious, did it hit the shoulder bone on either side?
What did the bullet look like on recovery, was it well mushroomed but still all in one piece, or had it fragmented and blown apart inside the carcass?
At only 80 yds, I would guess that bullet was still going pretty darn fast. Which would probably explain you finding nothin but fragments. Would also maybe explain why I see more pass throughs (generally, our close shots are twice that far). IME, alot of bullets can be going "too fast" to do what they're supposed to do. They've gotta expand, but they've also gotta stay together in order to penetrate and give an exit wound that will bleed.
A bigger bullet surely does give us more room to play with though. Cant argue with that logic.