Will,
I think a lot depends on the amount of power you need to absorb. If doing electric and you have to carry a certain size pack because the next smaller one won't get you through the pattern but with a two blade you have say 25%ish excess capacity, you could try a three blade and see it you get that down to 15 - 18%. The three blades will pull more weight but they are heavier and could cause yaw issues. If the ship is light, it might not be much of an advantage. My understanding of the three blades is they are generally 1 inch less in diameter than the two bladers. Also good to get ground clearance.

Best,    DennisT
 

  Best way to tell is to bolt them on and test fly them. If you are flying electric, you know what your requirements are and will find out how each affects the motor and battery performance. Just putting on what your flying buddy uses doesn't mean it will work on your airplane as well. Flying will also determine what your lap times actually are and you can adjust from there. Two blade props are more common and cheaper, if budget is a factor and it usually is. The elite 3 blade props are not very abundant, expensive and take time to acquire. Props are something you can stay up all night and drink a lot of beer discussing the pros and cons of each.
   Type at you later,
  Dan McEntee

There are 2 reasons for 3 blade props. The first and most important on electric model is they have uniform gyroscopic moment. Our experimets show 2 blade rigid prop (carbon or wood) can damage those subtile bearing really quick. Bearing cannot be large on electric motors, especially not that which is inside the drum. Reason is induced current from rotating magnets in outer ring, so there are typically one large bearing on open side of the motor (out of the magnetic field) and two tiny inside. Imagine those micro balls inside and all is clear. 2 blade props strongly vibrate and it kills bearing quickly. Standard IC engine constructed to withstand vibration have no big problems with it, but still, I used piped LA.46 with 12x3.5 2 blade full carbon prop and it made visible free play in shaft plain bearing after may be 100 flights.

The other reason is smaller precession. Moment of inertia is smaller especially because of mass distributed on shorter blade close to center of rotation, so precession is smaller at the same RPM.

Disadvantage is clear: little lower efficiency. There is always possible to make equivalent 3 blade prop, but result always come to smaller RE number  and therefore little lower efficiency (equivalent 2 blade prop has either wider blade, or larger diameter running at higher velocity - RE is in both cases higher). That efficiency is more visible on props smaller than 12" at less than RPM 10 000. That means 11" props need pitch maximally 5" to be in good efficiency (>10000rpm). 12" is safer. 6" pitch is good only if diameter at least 12" or more (9000rpm).

Still painting