The 12 does not have a larger pattern than a 16 gauge nor a longer range. An IC or modified pattern is the same size regardless of gauge. The only difference is the pattern density if you're shooting a larger payload in one gun over the other. If you shoot a one ounce load out of a 12 or 16 the patterns will be the same density and size at the same distance given the same choke size. Where the 12 outshines the 16 is in payload. You can easily shoot 1 1/4 oz. shells and larger in the 12 but you're pushing it with the 16. I personally shoot 1 oz. of shot out of my 16 for all upland birds. I shoot 1 1/8 oz. of 5's, though.

I spent all day Sunday shooting 30 patterns of different chokes and shot sizes out of two identical 16 gauges and two different 12 gauges and everything I said above proved to be absolutely true. I will also say that not one of the shotguns had a decent pattern at 40 yards with a modified choke. We did not shoot anything larger than a modified, though.

The 16 gauge shell is getting easier to find but your choices are severely limited. I would not recommend a 16 gauge as a primary gun to anyone that doesn't reload. Most factory shells are loaded to maximum and will knock the snot out of you.