Not enough detail in the picture to make a good judgement. So lets work with what we can see.

Muffler: rectangular cross section is better. Attenuates sound better and gives more volume with similar outside dimensions.
Crankcase: Looks like ball bearing to me, especially at the front.
Carb: Looks like a 2 needle FX carb.
Cylinder head: 4 bolts just like Supertiger has been using since the '80s. More cost effective without a loss in performance.
Price: Japanese stuff usually costs less in the US than it does in Japan, especially when you consider mail order discounts. No one sells O.S. engines at retail.

The FX series is coming up on 10 years - the normal life cycle for a typical O.S. engine design. I wouldn't be surprised if the AX series replaces the FX series. Wouldn't be surprised if it outperforms it, too.