I shoot both...BPS 10 ga and an Xtrema II 3.5" 12.
I would 100% reccomend sticking with the 12ga.
Why?
Well....it is true that a 10ga will throw a denser pattern than a 12 with the same amount of shot, and the 12 is more prone to stringing out the shot pattern....*but*
With a properly patterned 12 you are not going to notice. I mean, a top level competetive shooter may be able to tell the difference, but for all practical hunting purposes they are so close they could be interchangable.
Other considerations:
Weight: 10 gauges are HEAVY.
Ammo cost/availability: Premium 12ga ammo is a bargain compared to even moderately decent 10 ga stuff.....and you can actually find 12 ga when you need it.
Flexibility: I can shoot 3 1/2" BBB for high flying geese, slap in some 3" #5 for ducks, switch it up with 2 3/4" #6 lead for bunnies and then do some skeet with 2 3/4" #8.....you just cant get that much versatility with a 10
In short: If you don't mind a heavy gun, cost is not an issue or you love reloading, and you can afford to buy multiple guns for each application, get the 10....but from a purely practical standpoint a 12 will serve you better.
Oh yeah: Turkeys......you don't need a 3.5" for gobblers.....that's just marketing. I've limited out on birds every season since it started, and have never used anything but some old 2 3/4" high brass #4 lead I needed to use up. Turkeys are generally close, arent moving real fast (generally standing still) and are easy to kill. Find a cheap lead load that patterns well in your gun and just use that
