Kirst offers both versions, last I knew, a gated and ungated version, R&D's is ungated. Pros and Cons to me vary depending on the gun involved.
For a Remington, loading and unloading is actually faster ungated, by removing the cylinder, separating the backplate and ejecting empties and reloading, reassemble the gun. To use the gate, like a Colt SAA or Remington 75, you must eject each fired case individually (presuming you have an installed ejector rod) and reload individually.
You can unload/reload a Kirst gated by removing the cylinder as well, if speed is needed.
With the colt cap & ball, removing the cylinder is a much more tedious affair, removing the wedge and drifting off the barrel before removing the cylinder. On the open frame Colt type, a gated version, made by both Kirst and R&D, is faster and easier, as well as more authentic.