I would suggest that you download the demo from [link=http://www.reflex-sim.de]Reflex[/link], watch a video of an RC Helicopter doing 3D, and then compare it with the 3D demo flight on Reflex.. You will "see" that the heli on Reflex reacts very close to the real thing. I used RealFlight G2 (sold it now) before buying Reflex. After getting my Reflex and using it exclusively for a few days, however, found that I just couldn't go back to G2. The flight reactions/physics in G2 felt "stiff" and seemed very much like a game rather than a simulator when compared with Reflex.

I've also heard that the physics on XTR (Reflex v5) has been improved, so I wouldn't worry that it will be less realistic than Reflex v4.