Just about all the serious heli pilots in my area use Phoenix. Buy it once - all upgrades are free via download. I started with a Rev 1.X and am running 2.5s now. BTW - I used to swear by AFPD for planks, but Phoenix now has some pretty good flying planes so I am firing up AFPD less and less now.

RF - I started with version 2, went to AFPD and never went back to RF. From what I've seen at the LHS even RF 4.5 is not to my liking - I can't see RF 5.0 being much better.