Many years ago, before MSFS came on the scene I contemplated switching to P3D for that reason but, to be honest, with a huge amount of addon aircraft and scenery in FSX, I didn't want to hassle of having to reinstall (or if necessary buy) them again for another platform. So as I had a pretty smoothly performing FSX and was very happy with it, I decided to stick with FSX until I was forced (by hardware failure or whatever) to purchase a new rig or reinstall it. That situation still hasn't arisen but when it does I will now also have the option of MSFS and would have to carefully weigh up which platform to choose, bearing in mind that none of my FSX payware addons would be usable in MSFS where as some might be in P3D. Could be a bit of a dilemma but at least, for now, I'm still happy with my FSX setup!
Bill