As mentioned above, pick your load and then pattern at the ranges you expect to actually shoot a bird. You can only determine what is best or works to your satisfaction by use of a patterning board using your gun, choke, and load. I use a different choke when I'm hunting in the woods than I do hunting a field as the range in the woods may be under 20 yards while the field may be 40 yards or more. I much prefer a dinner plate sized pattern at 20 yards than one baseball sized at close range as it allows for a little less precise shot placement which can be very important at very close range.
I use a 12 ga but my wife, friend, and grandson use a 20 ga for turkeys. In the woods the most used choke is Improved Cylinder (.010") and for more open areas an Improved Modified. (.023") as measured from actual bore diameter. The same chokes in a different barrel may have a slightly different constriction due to manufacturing tolerances as well as other variances due to manufacture. With old Remington Hevi-shot loads of 4s and 6s the mentioned chokes have worked well for us.
