This is a personal question. Either caliber will kill deer effectively. Both are excellent at longer ranges and carry enough energy.

I will give you a confession from a reformed "use enough gun" believer. I once used 12 gauge 3 1/2" shells for duck and turkey. Used a 300 Rem Ultra Mag for deer. The heavy, fast loads killed everything quickly and cleanly. Only used these because they didn't make 4 1/2" 12 gauge shells and was too cheap to buy a .416 Rigby.

Killed deer, ducks and turkeys for years with these loads. Then one year I started missing. Spent hours looking for deer I knew I had killed. No way I could have missed but no hair, blood or anything but running tracks. Ducks flew in the decoys and left untouched.

When I sighted back in the problem became apparent. I was flinching. Nothing wrong with any of my guns. Shooting low and left with everything.

Rehab was simple. 3" 12 gauge loads work just as well. Bought some "chicken" (reduced recoil) loads for my 300 and shot bricks of .22. Deer now die again and ducks fold in the decoys.

If you want a new, big gun then go for it! But be mindful of flinching as you shoot.