i only have experience with the QD bipod mount. for my purposes, i think it is worth the extra money. put the mount against the rail, flip the switch. done. exact same tension every time. no chance of working itself loose.

if you don't want to spend the extra cash, then i would say go for the one with the knob. that would probably be good enough... you can still put it on and remove it pretty quickly.

they also make a type of mount that you attach to your rail semi-permanently using an allen screw. the harris bipod (the one brand i can speak for) is designed so that you can attach it to that type of mount as well. when you remove the bipod, the mount stays on the rifle (or you can remove the mount with an allen wrench) . to me, it is fiddly and it doesn't fit my needs. maybe that isn't a big deal to you, but i would avoid it.

just my 2 cents.