Barrel length will effect two things, how the gun balances and how it swings. Neither of these really matter when shooting turkey because you don't shoot them on the fly, normally any way.

It is true you might get a bit more velocity out of a longer barrel, but not enough to effect anything, and it is minimal anyway.

I like a short barrel myself because it is easier to get through brush with and will be lighter. Barrel length does not effect the pattern, that is dependant on your load and choke choice.

Shorter barrels tend be louder though, at least it seems that way to me.

Also barrel length on a shotgun can be a bit decieving. It depends on the type of gun you are talking. You have to take into acount the length of the action as well. If you have a 26 inch break open gun and a 20 inch auto or magnum pump they are actually about the same length because of the length of the action.

In the end pic the gun that fits you best and feels right in your hands.

I personally wouldn't waste the money on a special purpose turkey gun.

Paul