ORIGINAL: Eagle Al
If you like photographic images, then you have picked the right simulator, but if you want to learn the mechanics of flying your model with reasonable processor and memory requirements, FMS can't be beat. Also some users just don't have the bucks to fork over for the software and a powerful computer.
Utter tosh! While XTR, AFPD (and to a lesser extent RFG3) may well have "eye candy" their MAIN selling point is that they have very accurate mathematical modelling of the physics of a plane so the thing on screen "feels" pretty much like the real thing. FMS is great as an entry level tool for learning orientation and basic stick control but while a person could, for example, learn to hover a heli (including nose in) in XTR and then actually go out and do it on the real thing (I did!) there is NO WAY you could do that with FMS.
The one thing FMS has in its favour is the price. I guess the availability of third party models may also be an advantage but there's quite a lot of those for AFPD and XTR as well.
Cliff