Adam, Sure there are alot of differences between the two, many of which have already been outlined.
MAP senor inbuilt
laptop software
more map sites than the PowerFC
airtemp compensation
inbuilt boost controller
able to control large injectors, unlike PowerFC
rotational idle, anti-lag
programable output's
extra inputs
able to switch between maps on the fly
Hope that outlines some of the reasons it's better.