Druin's rotary is used for LS30's and any rotatable joysticks that clicks to 12 locations.
Opti-pac is for happs rotary where the stick is optical... ie, like a mouse. Spins and has some presision.
the happs optical is a more practical solution in that it can be used on any game that uses a mouse. Ok, driving games, ok for arkanoid games, ok for heavymetal games. But not great for any of them. (I don't think any arcade game ever used one)
LS30's are great for only some games. You can get it to act like an analog games for some... but not that great. But for the games that used the LS30 you wont find anything better!