While I haven't used the happ ones, I have built a couple DIY rotary joysticks over the years.
I like the ones with detents (switch version) much better than the optical version.
With the optical version, it's not as easy keep your guy locked into an angle.
The detents make it feel like you have much more control.
They don't even need to correspond to the player angle.
Some games had 12 positions, others had 8.
Just turning it until you feel the detent for the next position feels correct even if you are turning the joystick less or more than the original stick would have moved.
So what I'm trying to say is that I prefer the switch version over the optical disc version for rotary joystick games.
The optical version would work better if for spinner or steering wheel games.