The MkIII Trooper is a "J" frame, larger than the Python's "I" frame, and closer to the S&W N Frame.
The action is an example of the "S&W v. Colt" argument that's discussed ad infinitum on a number of web sites, and has been around for years.
Colt's "stack" continuously until the sear releases; and S&W's stack up to a point and then stabilize before breaking. Both are acquired tastes, and both have their allies and detractors.
The MkIII guns do have an "Achilles Heel", in that they shouldn't be dry fired without snap caps. Damage can result, and Colt is the only company that can repair them. The actions can be slicked up, but with a serious shortage of spare parts, one should probably proceed with caution.
I have a MkIII built in 1970, and it's a great gun to shoot. Not as smooth as my Pythons, or my pre-MkIII Trooper, but smooth enough.