Some like flippers some don't, for me it depends on the blade design. I like to open blades with my index finger, and carry tip up, it's fast and secure IMO being my thumb and 3 fingers are controlling the blade instead of having to draw it, then shift it to my palm and fingers. For this reason I don't care for thumb studs, too easy for a finger to slip, the spyderhole completely outclasses studs in this regard, far easier to flick open, it also doesn't get in the way of cutting.
Axis lock, BB lock, and the compression lock also give the choice of releasing the lock detent with the index finger and flipping it open without having to touch the blade, they tend to be really strong locks, and allow a blade to flip closed just as easy. Flippers are better than thumb studs(although most flippers have both), but not as versatile as a lock that acts as a detent, I especially appreciate them on framelocks where they serve as a large guard to keep your finger from sliding on the blade, and a stop to keep the blade from closing on your hand as you deactivate the lock. The PM2 doesn't require you to put your fingers in the way of the blade, or even touch the blade opening or closing, although the spyderhole does allow you to open it slowly and with good control if you want. The design also serves utility well with the 2 finger choils, big enough to keep your finger from slipping in the handle choil, yet easy to choke up to the 50/50 choil for detail work. A flipper between them, assuming one could clear the lock mechanism in the first place might get in the way of the 50/50 choil and would take away from the design, you would give up a lot in order to get a redundant 3rd opening method.
The bronze bushings when broken in and adjusted properly have no blade play and practically no friction, about the same as a bearing system, although once a detent on a lockbar pushes the blade to the side and creates some pressure a bronze bushing does have more friction than a bearing system, although it doesn't add nearly as much as the detent sliding over the blade. If you push the lock on a PM2 that has been maintained and broken in, the blade should flop open without any friction, bearings add cost and complexity, they are also thicker than PB washers and need more of a gap, or to be countersunk between the blade and liners/frame. Like a flipper, a bearing system is another design feature better suited to larger framelocks.
The different kind.
