It seems like, in the world of stunt anyway, electric motors are producing the same power as piston engines. So why would they need different props?
A few years ago, electric motors were weak, so they could use light, thin props. But times have changed. Can they still get by with weaker props?
Less vibration. A 2-stroke engine generates one honking' big torque pulse per revolution -- a 4-stroke (and probably a 2-stroke running in 4-stroke) produces a honkin' bigger torque pulse once every two revolutions. Depending on the construction of an electric motor it'll generate torque somewhere between utterly smooth and a whole lot of pulses (probably several dozen, but I can't work it out in my head) per revolution, each pulse being proportionally smaller than from a 2-stroke. And, a single-piston engine will always and ever be imbalanced. I'm not sure how that reflects to strain on the prop, though.
Igor Burger makes CF props that have moderately thick blades and some sort of core -- I'm not sure if it's balsa or foam, though. He dis-recommends them for IC.
Someone, whose name I can't remember, was using big quadcopter rotors for props on his electric stunter -- they were fine in the air, but much less robust than regular APC electric props when they suffered a ground strike. He lost a blade in practice for the 2014 WC (2012? someone help me out with names and dates please). That created a honkin' big imbalance that ripped the nose of his airplane off. He got a loaner plane, but finished well into the middle of the pack.