A Place For the 16GA.
The article (link) posted by ATLDave brings up a good point. While the 20 and 12 both have a place, and I own both (SKB550 20ga. and Ainsley Fox 12 ga. Sterlingworth), I still love my Ithaca Featherlight 16. The Fox goes with me for open country pheasant, and the SKB is a nice little woodcock gun, but the Ithaca was my only shotgun at first
It's light enough to carry all day in tough cover, throws enough shot to get that grouse before he can duck behind the nearest tree, and will knock down a mallard that I "jump" while walking alongside a stream. Yes, I can get as much shot and velocity from a 3" 20ga., but the tube is smaller, and the shot string is longer. It's easier to miss a 50mph bird with the 20 ga.