Sorry but, there is a difference. I took the plunge few days ago cuz i've had it with FSX. I can run it with all sliders to max, which i couldn't do with FSX. And it is much more stable. I get 30fps (unlimited with an external limiter) with the NGX 737 (oups sorry PMDG) at a complicated airport where it use to be a slide show with FSX. Plus the scenery is crispier (more "warm"?). But the stability! Even at Aerosoft's Heathrow with lots of traffic, i get 18ish but still smooth as butter. And don't forget that you get support from a very good team and they are improving it regularly. I'm got the Prepar3d upgrade from Just Flight's Traffic X and it's very good.
Hey, i have traffic at FSDT PHNL...