The DF65 is a one design class within the RG65 class, sort of intended to keep costs in check. The lack of restrictions on construction in RG65 has ensured that what could and should have been a low cost class almost instantly, because state of the art technology was used from the off, went straight into big chequebook territory. When you consider that any "65" is basically a half size Marblehead, it should not be amazing that the developments that pushed up costs and prices in the large class should have been applied immediately. There isn't a market for mediocre boats - they are purely for winning with, so there is the one design end with relatively low costs and somewhat restricted performance, and the rest, with performance at any cost. Unless you happen to be good at designing and building extremely lightweight hulls.
A properly set up and sailed DF can beat an RG, but probably only if the RG skipper thinks that just having his type of boat makes him a winner without regard to being able to set his boat up and read conditions on the water. Racing isn't always simply about top speed. Racing yachts don't simply go fast because of their design or build, there is setting them up for the conditions on the day and knowing how to sail them and reading how to position them on the water to best advantage.