I would have to gracefully disagree with Floyd3 that the 12 will do everything the 10 can do. Having carried all of the gauges from .410 to 4 gauge afield I can attest that the best "all around" gauge is the 10. I could make a strong case for the 8 gauge but it is not mainstream so I will stick with the 10. The 10 patterns better than a 12 and can carry a bigger payload if needed. Yes, if we are talking store bought ammo with a modern gun the 12 makes much more sense. But if we are talking vintage guns then the 10 is hands down the king. Those who know, just know. I own more 12's than 10's but I prefer to shoot the 10 at almost everything. Even at quail, a 10 loaded with 1 1/8 ounce of shot is a joy to shoot. I can also put gauge reducer inserts in and shoot 28, 20 16 and 12 gauge if I wish. But the magic of the 10 comes with using real black powder.
