Galen,
Your answer requires a CAVEAT. If you are talking about closest to the original Sample Example in appearance, a little nod will go to Uberti.
If you are talking mechanically with the thought of using the gun for CAS, PIETTA hands down. Pietta is much easier to set up for the CAS game. You also get a very wide selection of Barrels and build materials. Many more options.
Now for the other CAVEAT. Which ever you select, to be even remotely useable for CAS, your going to have to do some serious work to make the gun reliable enough to play the game. There are NO Cap Guns ready for CAS right out of the box.
PS: Forgot important point. You even get to choose CALIBER with Pietta.