Each has a plus/minus. The Anvil is very sturdy and smooth panning with a rifle, you can use an Arca type plate or a Pic rail. The RSTA is also very sturdy, it has a larger lever for locking/unlocking and pans well. It's much more bulky that the Anvil and is limited to the Manfrotto plate. If you don't have a good plate mounting system on your rifle, that can be a weak point. the DCLW is even more bulky and in my view, a bit harder to adjust. It's Pic rail only.
None of these are very goo for a spotting scope, though they can be used. The Anvil is what I'd use if I had only one.