OK. So after reading some of the excellent posts above, I'm going to flip flop on this one.
As we gain experience, the way we gain experience, is by having those "oh $hit" moments. Maybe the reason it is easier to get insurance on recips is because generally, those "oh $hit" moments happen at lower altitudes/airspeeds.
The King Airs that I have flown have all been much easier to fly than the old Chieftain I flew years ago. However, they are less tolerant of mismanagement or errors made by the pilot. Also, the trips were much longer and complex, requiring more planning.
I guess a properly supervised 1500 hr pilot, flying a C90B between Raleigh and Charlotte would be OK. But, I would not be comfortable throwing him into the Rockies in the winter.