We tried the 2 leg or Bi-Pod for several years. We didn't find sufficient elimination of movement with it so we added an additional set of arm jacks at the rear of our 38'Carriage but still had unwanted movement. It wasn't until we added permanently installed stabilizers, which we attached to the 4 corners of RV, almost 8 years ago, that we achieved success. Once the jacks are lowered and the rig is level, tightening the knobs gave us virtually no interior movement.
I think some of it depends on what type of RV'ing you do and what you want to achieve. For some, interior movement isn't a problem but being fulltimers I wanted our "home" as stable as possible. If some movement doesn't bother you or your are an occasional Rv'er a bi or tri-pod might work for you. Another bonus for us is that we don't have to take anything up or down or find a place to store it. hugs, Di