If you have already bought p3d, then I would definitely NOT buy fsx (steam or not). I consider those products for obsolete and dead, in the sense that they will not be developed any further. Dovetail reveiled their true nature not long ago by announcing their Xbox "sim" - the future path of FSX steam should be quite clear to us all. Sure, the steam version might receive bugfixes, but that is fixes to the existing code, nothing new. So, to sum up; in my world only two viable Sims with a future exists: P3d and X-Plane...