I'm looking to buy a new graphics card for a single card gaming rig. $200-$250 is my ideal budget. My specs are:

E8400
4GB RAM
(7900GS)
Corsair VX550W PSU
1680x1050 22" LCD

I primarily play FPS and RTS games.
What would be my best option?

Performance is basically the same, they edge each other out in about the same number of benchmarks. I would buy the 4850 myself, I tend to prefer AMD cards to nvidia. I think the 4850 runs a little bit cooler too, it does use a single slot cooler compared to the dual slot on the 9800GTX. Really, since price and performance are pretty much the same, it doesn't matter much. I would say it boils down to if you have a brand preference, and whether or not you mind a dual slot cooler.

im going with 4850 for me on this one-

1) its here now
2) drivers will improve (9800 has little chance because is just an oc 9800)
3) cheaper (can get it fro 170bux in the US)
99) Give the underdog a chance!!!!

Another one that I'd add to your list is that the 4850 will easily fit in most cases, while the Nvidia cards are extremely long and can be hard to it in many cases.

I say go for HD 4850, it delivers better performance than a 9800GTX in almost all games and it cheaper

In addition to everything alrdy mentioned 4850 is 55nm and 9800 65nm.

If I were you I'd wait till 4870 is released, I think it'll cost less than 300$ so is a good option.

Actually, I've seen that the 4850's run quite hot...

Since performance is the same, I've been thinking I might go with a 9800gtx, for the dual slot cooler.

But then again, the 4850 has DX10.1, and a more forward looking architecture. At least I think...

Actually they're the same price now.

Thanks for that, i didn't know it because in the first previews i read, the HD 4850 was the same

So well both perform the same, but HD 4850 beats the 9800GTX (as i said) but the difference isn't much

of course 4850
you can oc the card to 700mhz easily by adjust the catalyz-control center
but 9800GXT is on a high frequence now

Yea wait a little while ATI partners probably will come out with a 1gb/with a better cooling solution

Apparently ASUS has just such a card that will be available in the near future.
http://img525.imageshack.us/img525 [...] x57fu4.jpg

Yeah, I can't wait to see how that does at 1920x1200 compared to the standard 4850

Plus the 4850 needs a lot less power, an aspect to consider if you have a less powerful power supply.

Also 4850 has excellent idle power consumption and excellent HD video acccelaration!!