RE: 12 or 20gu
The title really doesn't say much. There are a bunch of variables, like what are you going to use it for, how far do you expect to shooting with it, how well do you handle recoil, how heavy of a gun do you want? And on and on.
Price wise they will be about the same, both the for the gun and the ammo, And availability will be about the same. The 12 and the 20 are by far the most common shotgun gauges. Probably a bit more selection in ammo for the 12 ga in my area though compared to the 20. The 20 ga will be lighter and have a bit less recoil depending on the loads used. However the 12 ga can carry a larger payload than the 20, or send a same sized payload farther and faster.
For small game like bunnies, pheasant and the such I would say the 20, it will more than enough and easier carry and use in the woods. Now for Duck, Geese, Turkey or deer with buckshot or a Foster slug I say get the 12 ga because it will give you an extra edge over the 20 ga in payload and ammo selection.
And for small game I would even suggest something lighter like a Franchi over the 1187. They have a bit more reciol, but you don't feel it in the field and the lighter weight gun is much nicer to use and carry.
For shooting sports a 20 is fine for skeet but for trap you might want a 12 instead, although my girlfriend did pretty well with a 20 ga 1100 on the trap range the first time I took her.
My opinions and nothing more.
Paul