My direct experience is only with Impacts, but I've heard hearsay about the SV-11 and Blue Max, namely that they are both excellent stunt planes.
Impacts work well with various powerplants: OS .40VF, different sizes of PAs, and RO-Jett .65s among piped engines, Saito .56s and .72s, Supertigre .60s, and a bunch of electric systems. As for being difficult to fly, I flew one that won the Nats that I thought would make a good trainer.
If I were to choose among individual examples of the three, I'd go by how accurately each was built and by the quality of the control system.