Gary, the Bolly is a unidirectional carbon prop with solid blades (fibres run continuously from tip to tip - extremely strong, but heavy too)
The Mejzlik is a mix of carbon woven cloth and some long fibres (on the back) and the blades are hollow like model heli blades.
As far as I know neither makes a wood blade (but I know a guy that may copy them out of maple to try out next season
)
I agree with Kevin, treat yourself and your engine to a nice prop. With the larger planes you dont break them as easily (nosing over is a lot less likely)
The manufacturer should recommend a size to try first, they should know what they are talking about... or talk to a guy like Mike Clemmens that both makes props and also flies them, and is around many guys using the different sizes of engines. I like his design a lot, it is a good prop IMO.
As far as flexing, sure, the carbon props are VERY stiff and especially the Bolly. A good wooden prop (made from a good selected piece of hard maple or beech) will also be very stiff but a wee bit more prone to flexing. I dont think it makes much difference myself.