If you want quality and stability with DX9 games and are in to filtering then the 9800 pro is your best solution.
yup, my thoughts exactly. 4xAF makes a huge difference now sinse texture quality is so high in newer games... couldnt imagine playing without it really i mean you dont get a card with a 128meg texture cache for nothing
Um, a little more info would help us in giving you advice.
Is MS Flight simulator 2004 really the only game you will play? How about a few first person shooter games (Call of Duty, Unreal Tournament 2003, Halo, etc)? Direct X 8 or 9 gaming?
For instance, if you are like me and want a card that will run Doom 3 best, the GeForce card appears to be the better choice. Id has suggested the game will likely run faster on the GeForce line.
How important is price? The Radeon tends to win in most benchmarks, though the GeForce card may be a bit cheaper.
Do you like running games with anti-aliasing and anisotropic filtering on? Again, the Radeon tends to be a bit better in terms of image quality and performance with these options turned on. Also, 128 mb cards are a better value rather than 256 mb and will give the same performance unless you run super high resolutions combined with these options.
Oh, and let us not forget the Direct X 9 debate that rages on and on. In case you are not familiar with this, here are the highlights:
"blah blah blah blah, Radeon better in Half-life 2 beta, blah blah blah, Nvidia engineer sick on Direct X 9 test day, blah blah, Canada rules, eh?!!!"
I may be missing some of the details here, but I think that covers all of the major points of the Direct X 9 debate.
And finally, if you are really thinking high-end, consider the 5950 ultra rather than the 5900. It may only give you another 5% performance advantage, but if you want the best Nvidia has to offer regardless of price, consider it.
Good luck in your shopping. I'm sure you will be happy with your new system as these cards are all pretty great!