I had the same dilemma and I wanted to go for the 111 since it is manual-wind and historic and I like the engraved movement the older ones had. I put the 312 on my wrist and I loved it. It made me smile more than the 111. Simple as that. Later I bought a 111 and sold it. Same with the 233 and a few others. The 312 will always be my first Panerai and I hope that I never have to sell it. It wears a little higher than the 111 but to me it is very comfortable. If you are going to wear it as a daily watch, the quick-change strap system will make your life soooo much easier (if you like changing straps) and the date is useful. It is my daily wearer and I love it!
Good luck with your decision; they are both great watches so you can't really go wrong.