James,
I get to fly
alot of RV prop/engine combinations and compare performance and have tested 9 different props on my RV-4 and RV6X. Alot depends on your budget and the type flying you enjoy.
0-320 the 2 blade Catto, MT and Hertzler provide slightly less climb but are faster in cruise than the three blade Catto and PP. Only Margie Warnke's Three blade
Claw is faster than 2 but she is retired. The 3 blade Catto has and still is an absolute work of art and is a bit smoother. However comma, the new Catto 2 blade I am currently testing on my 0-320 is turbine smooth. See previous thread.
0-360: The Catto three blade excels on the 0-360 with excellent performance across the board. If you have lots of $$$ the Hartzell BA C/S is a phenomenal combination on the 0-360. Craigs three blade however will match it in cruise and efficiency above 8000'.
IO-540 The Harmon Rocket excels with the Hartzell HCY "Paddle" (mine had the "D" twist) two blade. The "J" twist blades are optimized at 2300 RPM, the D 2500. Several Rocket guys using the WW three blade report excellent performance. The MT three blade is slightly slower but excellent climb and smoothness. The RV-10 prop of choice is the Hartzell BA two blade in my humble opinion. Tom Martin has a derivative on his F-1 reporting impressive numbers as well.
A long answer to a short question...

Smokey