All I have is the swivel, notched leg version. Sold all the others I had. If it says anything, Triad Tactical said they only carry the swivel, notched leg versions of the Harris bipods simply because they believe it is the best option and not worth dealing with the hassle of the others..
If you go swivel get the KMW quick release handle it is awesome. I have one for each of mine. Look up Steve at Triad Tactical he will hook it up and is a great dude to deal with.
We have recanted on the statement about only carrying the notched leg version. We have heard from enough people that have valid reasons for perferring the smooth legs to start carrying them. Here is a video you may find helpful: