Re: best gearbox?
I have the Stage 2, but the internals are the same.
The Grubee has a freewheel built into the gearbox sprocket so assuming that the rear wheel itself spins free, it should coast much better.
As for noise, some have experienced some gear noise and I did early on, but the engine was always the more prominent noise. With grease in the gearbox, I do not have gear noise any more. Over all, I think it is clearly better than the "Hoot". Some have mentioned shaft length issues with interchaging the boxes, but I don't know anything about that.
BTW- I have heard all good about the Huasheng. It makes a bit less power than the Honda, but all seem to agree its a good engine.