I have the 835 but with a pistol grip. The thumbhole / pistol grip really help with reducing felt recoil and accuracy. Only down side to the mossberg with either of those stocks is the location of the safety.
The safety is located on the tang of the weapon. Works great with a traditional stock cause your thumb is right there to work the safety but with the pistol grip or thumbhole its a little awkward to work it. Nothing to crazy and since your only using it for turkey so you usually have time to remove your hand work the safety and your good to go.
A safety located on the trigger guard like the 870 is much easier to work with a thumbhole or pistol grip stock