This is a great question. One that we've brought up many times, and nothing ever seems to change.
We've been using the Delta V15 rotors, but it's very clear they are NOT the most effective or efficient. We've tested a few others, but more testing is needed. If you've got ideas, try them! Or send over design files and we can 3d print them!
From what I've read in previous threads and the internet, the higher the fin count the higher the efficiency, however it probably doesn't allow for as high RPMs as the 5-blade. I saw someone in the thruster design forums that made a test rig out of acrylic, but never saw any results from them.
I guess I'll go with the 7-blade ones.
Edit: For some strange reason, the original post didn't include the description I had typed. It essentially asked whether to use the 7-blade props from hobbyking (in the orignal BOM) or the e-flite ones. In addition, I asked if I should even bother getting a micro servo from hobbyking, as Eric mentioned in another thread that it didn't really work as well as you guys wanted. What are your thoughts on that?