Dennis,
Thanks for the information on the APC props. Looking at it there multi rotor props would be within rpm ranges that we would use for 5.5 - 6" pitch up to 12" diameters. The quadcopter carbon fiber props should match the APC's but since there are quite a few suppliers some may use weak resin. Seems the price range is all over and my gut says the lowest cost is likely not the best choice. From another thread it seems that the failures have been after a strike, which if that happens you would (or should) check the prop condition regardless of the material of construction. To some degree you want the blade to break if it hits something. If the prop blades are to strong then the motor shaft could be damage (bent or set screws slip) which could be very costly. This all come down to common sense at the field, check the whole ship over before you fly looking for things that could be unsafe or result in an uncontrollable model, same as full size aircraft pilots do before they fly.
I hope Matt and others will post some information on the brands they are using.
Best, DennisT