From a competition pilot point of view there would have to be a small drag penalty and a weight penalty. But both of those would seem to be pretty small in comparison to the competitive benefit that arises from the ability to stick to the course line and never have to be distracted by the need to deviate towards a landing option. I don't have experience to know, but I'm suspecting that the reliability of the FES might be sufficient that one could drive it straight into the boonies then flip the switch only at the last minute -- wouldn't that be exciting? You certainly can't do that with a gas engine.