I have both Phoenix and G4.5. I mainly fly helis, and have found that g4.5 is more realistic. But it certainly isnt twice as good as Phoenix.
G4.5 also requires a super compter to run it
So my pick is Phoenix, half the price, will run on just about any computer and updates are free.
The graphics are good, not as good as G4.5, the physics are good, not as good as g4.5 but certainly up there on both counts.
my 2 cents.
Darin