I voted for the 16ga, but its really dependent on what you are doing with the gun and how into reloading you are.
I've shot probably over 10,000 rds through my Sweet 16 and have found it to be fully capable of anything you can think to do with a 12ga, albeit at a slight reduction in range due to only being able to shoot 2.75" shells. Also, my Sweet 16 with its 28" FC barrel seems to have the perfect balance I like in a gun. Its not muzzle heavy and swings with a very fluid motion & feel.
However, those pros come at multiple drawbacks. The Sweet 16 is recoil operated and it kicks like a mule every shot. I can't number the times I've come home from the range after a case of shells and seen the FN logo from the buttplate bruised into my shoulder. Lighter loads cure this issue, but then you might need to adjust the recoil spring in order to ensure the action works properly.
Ammo will be expensive if you don't reload. A case of Federal Game Shock Hi-Brass 1.125oz rounds that I shoot clays with is $120-$140 ($12-$14 a box) and its nearly $300 a case ($30 a box) for the Federal Wing Shock Magnums I hunt with, but you can find shells from Winchester for clays & birds for about $76 a case ($7.60 a box). I wish I had spent more money & time learning to reload than ordering ammo.
Chokes are going to be an issue. If you want a different choke in the Sweet 16, you have two options: buy a full set of barrels each with a different choke or call FN and have them custom make an Invector-Plus barrel with a full set of choke tubes for the gun. Neither option is cheap.
Cost of ownership is another issue as well. Parts for a Sweet 16 aren't exactly easy to find and they are going to cost a lot to buy either from someone or have FN remake it.
The only gun I like as much and have shot as much as my Sweet 16 is my Gold Fusion 12ga. It suffers from none of the drawbacks of the Sweet 16, but its not as balanced or swings as fluidly as I would like. Its gas operated and has a recoil pad in the buttstock. This kills almost all of the recoil from even heavy 3" mag deer slugs. Ammo is dirt cheap as you can go to Wal-Mart and buy a case of shells for about $30 and the action needs no adjusting for light or heavy loads. The gun uses Invector-Plus chokes so its next to impossible to not find a particular choke for it. And its new enough that you can find parts for it readily from Browning.
I can't comment on other manufactures 16ga's. Hope you find this helpful