Interesting article in Flying by Avemco. Their study on piston GA show almost no difference in accident rates in piston GA regardless of license/rating held and number of total hours flown. What it did show was time in type (over roughly 200 hrs) and currency is what reduced accidents. I am sure there would be disagreements, however since Avemco only insures piston GA, they have quite a bit of data from their own records.