Plenty of info here...
http://www.avid.com/us/products/fami...-Tools/compare
Some highlights.
PTHD 9
48 bit fixed mix engine
TDM Plug ins
Heat on mixer
160 Channels simultaneous record
PTHD Native 9
64 bit floating point mix engine
No TDM Plug ins
No Heat on mixer
64 channels simultaneous record