RE: Which 870?
The 870 is a fine choice for turkey, dove, etc. The short barrels will work fine for all bird hunting. However, the choke tube you use will most likely have to be different for each type hunt. i.e. you can't shoot steel shot (needed for waterfowl) thru some choke tubes, thus requiring another choke tube. Most companies make all types of choke tubes for the 870. Also, with powder designed and used in shotguns today, all the powder will burn before leaving the barrel.
I used to hunt with a 870 in 20 ga.3 inch mag. Took many turkeys and ducks with that little gun. I use and believe the 12 ga. 3 inch mag. is plenty for turkey, which is what I now use. The 3.5 inch will definitelydo the trick, but just a little more punishment that I don't like.
dog1