I had used the medium because the large was very slick. I did the stripple on just the back and it works way better now.

I use the large with grip tape on the sides, front strap, and back strap.

It doesn't move around in may hands.

Medium if on a hot day so it doesn't slip. Otherwise the rubber coated large.

The small is wayyyyyyy too small for me.

I don't really notice a difference, I shoot them just fine no matter what. Mine was a gift for the GF so I am not even sure which one she has on there now.

Medium (the one that says sig pro on it) or the large that has parts of it covered in rubber.

Large. One of the few factory grips that get big enough for my tastes.

Currently the small is on the 357 Sig and the original medium on the 9mm.