From personal experience, Phoenix is a fantastic tool. While they are NEVER exactly like the real thing (spacial understanding is never the same, and the physics of each model differ some form the real life model they are copying, but then no two aircraft ever fly the same), they do come VERY close, and will help with thumb control and basic flight principals & technique.
As for the DX5 - well that will bind to any of the 5 channel or less 'Bind-N-Fly' aircraft from Parkzone or E-flight, so if you have looked at them already, keep it in mind!

As for the ability to teach you, there was a national 3D heli champ here a few years back who spend a few months on a sim and with almost no real world time went out and won the nationals. That speaks for itself I think!!