I, too, consider myself well informed. I used FS9 for several years and was very happy with it. When FSX came out, I bought and installed it, but kept FS9 running so that I could do side-by side comparisons. Which I did -- I set up flights in FS9, ran them, and then ran the identical flights (same planes, location, weather, and settings) in FSX on the same computer. I did this repeatedly many times, over many days -- I was in no hurry. The end result is that I was blown away by FSX (default version, even!) and how far superior it was to FS9 in every respect. Among many other things, just the sense of realism in how things look was so far advanced in FSX over FS9 that there was no comparison. And this was just one aspect -- there were numerous other advances in FSX that demonstrated its clear superiority. After this, deleting FS9 was a no-brainer. I will add that I have a system that allows me to run FSX with most sliders maxed out and no FPS (or VAS) issues -- generally very smooth.
I respect your arriving at a different conclusion, but I have to think most other flight simmers have long since arrived at the same place I did -- just seeing the far greater activity in FSX vs.FS9 forums indicates this. But the bottom line is, we are both happy and that's all that matters.