SilverWook said:
I think the visual disconnect results from trying to make him younger. It makes little sense for someone several centuries old to look significantly different over a mere thirty years. That, and they used silicone skin versus the latex skin of the original.
Or else they applied the same goofy rationale later used to justify "fixing" the "flaws" of the original Vader helmet design for ROTS.
But if you compare Ep. V Yoda with Ep. VI Yoda, there is a noticeable difference as well. Yoda looks pretty bad in ROTJ, so why not make him look younger in the prequels?