I bought both my Harris bipods used for about $75 out the door at my LGS. The 6-9" HBRMS, updated with a Podlok and RRS ARCA clamp, has seen far and away the most use (the other one is 9-13").
I used my short Harris bone-stock for my first year of competition, attaching it to my rifles via adapters (MLOK/swivel stud on MDT-chassis'ed Tikkas, RAT rail/stud on MPA-chassis'ed custom). In terms of stability, the biggest benefit by far -not quite a necessity, but close - is to spend $30 for a Podlok.
I also have an Atlas BT65-NC CAL, which comes standard with a Podlok, and I put an RRS ARCA clamp on it also. It was a late Christmas present so haven't used it in competition, but I have quite a few hours' range time with it.
So my Harris and Atlas units have exactly the same tensioning and attachment functionality.
I don't get why people trash Harris. I find the stability difference between my Atlas and Harris units minimal, especially if you consider the $100-170 price differential. For competition, the Harris has a narrower footprint, which has been useful on narrow props. The Harris legs' spring-loaded up-down function has been useful moving from, say, the hood of a prop vehicle to shooting through the vehicle window frame. I'll choose the Atlas for pure stability when footprint space and folding aren't in play.
I've handled a Magpul bipod in a LGS but never experienced one actually mounted on a rifle... no real opinion.