i had a bit of a look at them, and the inside is the same. it just has 3 or so mm less steel on the outside. mine uses the xt's reg/rec and 2 phase stator and it runs a 60w halogen bulb just like the xt did.
a heavier flywheel helps you stall a bit less i suppose. someone who knows more might chime in, but the lighter flywheel in my case was no detriment.
Where you come from is gone. Where you thought you were going, Was never there. Where you are, Ain't no good unless you can get away from it.