Vista - 9800 gtx+ or 4870

hey guys i just got paid and i looked at my lil bros computer and he has the 8500gt and he plays more games than me and im thinking of getting him a new video card 250 budget his computer specs are
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01374052&lc=en&dlc=en&cc=ca〈=en&product=3686668
cheek that site for this specs its the stock hp computer but he has a 600w OCZ steamXmod psu witht he lights and he has the same monitor as me so is it better for me to get him the

XFX 9800 GTX+
XFX GeForce 9800 GTX + Video Card - 512MB DDR3, PCI Express 2.0, SLI Ready, (Dual Link) Dual DVI, HDTV, VGA Support PVT98WYDFH in Canada at TigerDirect.ca

or the

sapphire radeon HD 4870
Newegg.ca - SAPPHIRE 100259L Radeon HD 4870 512MB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Desktop Graphics / Video Cards

if anyone know any other good choies for this computer then feel free to add some suggestions im still new to computers

sounds good, the graphics card is definately bottlenecking the performance of that system, you wouldnt need to change the power supply, its more than sufficient, but with a budget of $250 (canadian dollars i assume), you can get a lot more than that 9800GTX+, theres another 9800GTX+ thats a lot faster, it looks like the same one but its far from it, XFX GeForce 9800 GTX+ XXX Video Card - 512MB DDR3, PCI Express 2.0, SLI Ready, (Dual Link) Dual DVI, HDTV, HDMI Support, VGA Support PVT98WYDDU in Canada at TigerDirect.ca
this will run most games at max resolution.
i cannot give you tips on the ATi/AMD as im a Nvidia fanboy

the 4870 is a killer card but it is all up to your preference although the 4870 has a edge on the other card you were looking at
but i am a AMD\ATI fanboy lol

together we will guide even the most noobish of noobs

lol we shall

Both cards are the same really, but I think the 4870 gets an edge when anti-aliasing is brought in to the equation.

So really it's all up to your personal preference like what's been said.

true....... their is the difference of stream processors
the 9800 gtx has 128
but the 4870 has 800

Yea there is that, too. But Nvidia make up for the lack of stream processors by having an independent texture fill rate, which balances it out between the 2 cards as well.

true its all up to your preference