Howdy Charlie,
The Army grip is longer, how much longer, I can't say, but your pinkie don't dangle on an Army grip.
The Navy grip is the same as that found on the Model P type pistol.
A Remmie grip has about a half inch more between the frame and the curve down to the plow handle, if that makes sense.
I have Army grips on my OTs and got them to shoot duelist, the grip seemed to fit me better than the Ruger Bisleys I had been using for CC, plus it was cool.
Adios,