ORIGINAL: paranoid
I dont know if the "royal bb" servo's or the IPD set up is better or not.
(nice set of 559dig's for my new heli sounds good)
Royal servos come both as normal and digital versions, check which you are being offered. Digital version have the word "digi" on the label on top of the servo. It's probably the normal versions, I have some they are decent servos, and you can spot the red Multiplex Royal and Jumbo servos on military target drones of most armed forces in the world because they are so reliable.
IPD is no better, no worse than PCM, it is a method of having fully programmable failsafe on PPM. The difference is you program the Rx not the Tx.
I have no knowledge of helis and therefore no first-hand knowledge of how the Evo copes with them, though I have met two heli fliers trading in JR PCM10 for Evo9 because they said it is supposed to be better, and they told me that Vario factory has said goodbye to its JRs and put the entire factory demonstrator fleet on to one Evo12. Apparently Vario make helis? But as I am not a heli flier the name meant nothing to me!
Harry