There's an article on the Raven II in the latest Today's Pilot (I wonder who wrote it....dum-de-dum). To quote from it...
"There are a few external differences between the Raven II and its predecessors, which Al now pointed out to me. The main and tail rotor blades have both been modified in the Raven II, and they have rounded aerodynamic tip caps to reduce noise levels. The rotor blades also have a wider chord, which means the new version is around five knots faster than the Raven I. There are two oil coolers, as the more powerful engine gets hotter and needs more cooling. The Raven II also has a higher gross weight, an increased payload, and the 28-volt electrical system means that starting is noticeably easier and more energetic than in the Raven I. And the simplest change could well be the one most appreciated by owners – the ignition key also opens all the door locks, eliminating the need for two separate keys."
There's probably more, but I can't easily separate it out from the whole article!