Cr flywheel is lighter. Less rotating mass makes it easier to start and rev quicker. I have yet to see any Dyno results showing increase of hp when using the cr ignition setups. I have never ran one, but there are many who swear by them.
I have used lightened flywheels on banshees and blasters, but I found they would stall out easier when I was heavy on the back brakes. If you are not blitzing corners or you have motor cross forearms, then stalling shouldn't be an issue. I tend to suffer from arm pump, so getting on the clutch can be a challenge during long rides.