I recently got a 512mb card for FSX.
It has improved performance by quite a large degree. However i was flying on my friends 2004 flight sim and what i have done is a small comparison.
He has a 128mb graphics card.
His airport detail in FS9 on a poor GPU is amazingly good.
My FSX detail at airports is terrible, so bland and no traffic.
His scenery looks highly detailed and runs smoothly.
My FSX detail is low and doesnt run that well, especially in cities.
The planes in FS9 definitely handly far more realistically than FSX.
FS9 will be making a comeback for me tonight, i know that i will be able to have everything on ultra high and it will still give me 25-30fps.
FSX will go back on the shelf - it is an empty shell of a sim, and simply cannot offer me any improvement over FS9.
I love my add-ons, my detail, my 95% traffic, my que to land and que to takeoff, my smooth flights and simply my FS9 in general!!
Just thought i would share all of this as it made my mind up for sure.
By the way, did i mention he is running FS9 on a laptop???
Noticable Improvements I have seen from FS9 to FSX
Improved scenery and some places look stunning
Cockpits seem improved
Water looks amazing almost lifelike
Missions are great fun although not to everbodys taste
My PC is a fairly decent 4400X2, 2GB and a 7800GT OC, but it really struggles in the certain parts of the sim. Flight simulor 2004 despite its age still looks ok specially with scenery add ons and is much more framerate freindly with current generation of hardware. FSX should see a good improvement with Vista and the next generation of Graphics cards.