I have X-plane (the latest version is 7.50, which wasreleased pretty recently)...and the actual flying is very different. Muchmore challenging, every litle bit of bump in the air is noticeable, it is not the same in FS2004, and here's why (I took the liberty to copy a forum post on x-plane.org)
"MSFS uses lookup tables and such to simulate the aircraft performance. Every Aircraft has to be completely programmed from scratch. They've been paying LOTS of attention to scenery, the sim looks great.
X-plane computes, many times a second, the complete physics model of the aircraft and airmass. It can model just about anything, from a flying paper clip to the White Knight and SpaceShip One.
MSFS = Pretty, flies "wrong," limited aircraft, easier for beginners
X-Plane = Not so Pretty, Flies "Right," unlimited aircraft, steep learning curve......
.....AFAIK, Only X-plane is certified by the FAA for logging hours toward a real-world flight qualification certificate. That's interesting to me."
And now when X-plane is capable of modelling full 3d matrices of air data, flying in turbulence is helluva challenge
