The GTS 250 is a re-branded 9800 GTX+.  Both are based on the G92 core.  The earlier versions of the 9800 GTX required two 6 pin pci-e power leads.  Both now have only one 6 pin connector. 

I have 9800 GTX+ on my Phenom rig, and they are solid performers.  I have Battlefield: Bad Company 2 at 50+ frames a second on high settings with AA @ 1x. 

That being said.  Its a really a coin toss.  I would probably go with the GTS 250. 

boredgunner

I'd go with an ATI Radeon HD 5750.  Better performance for around the same price.

+1

There is no perceptible overall difference in performance between an HD 5750 and GTS 250.  If you don't need DX11 don't worry about it.  As for the two models the OP has listed, the 512MB has a slightly faster shader clock, but it won't make much (if any) difference.  I'd probably go with the 1GB especially on resolutions greater than 1680x1050 with graphically intensive games.

Allow me to qualify the performance of my 9800 GTX+ with BF:BC2.  This is with a pair of EVGA 9800 GTX+'es in SLi with a overclocked Phenom 9850 X4 @ 2800 GHz (soon to be a Phenom II X4 940 Black Edition), 4 gigs of XMS DDR2 RAM, and Vista x64.  Don't try to throw a 9800 GTX at a dual core CPU and expect great things with that game...it simply doesn't do well.

I'm also not swayed by the performance of the 5750 in DX11 as compared to the G92 core in DX10.  I have seen some pix of DX11 and it is a definite improvement over DX10 (tessellation with DX11 cards is awesome).  But, would you really gain any FPS with a 5750 In DX11?  I haven't seen any comparisons recently, and it is not much if any. 

jmlahmon makes an excellent point. Depending on how long your planning on keeping your card(s).  The 9800 GTX+ with lifetime warranty might be the better deal.

The OP never mentioned ATI in his two choices !

The GTS 250 is the better card even without the extra Memory but TBH 512MB is poor today.

Don't see how the 9800+can really be classed as the better choice at $10 cheaper with 1/2 the memory.

I am a owner of a 9800GTX+ 512 and it runs everything I ever put at it.I would look at the warr stand point if I planed on keeping it for a while or folding 24/7.If It going to be short term(1 to 2 years) then I would go for the 250 because of the extra memory.For the ATI suggestion.I would not trade my 8800 gts 320 for a 5 series ATI card unless I had a buyer.I fold so ATI don't cut it for me.

I've just installed the EVGA 1158 as my primary, and my existing  EVGA N872 as my secondary, using it as a phys X dedicated GPU. Still trying to understand if my configuration will work. I am using two monitors, one is a DELL 2005FPW, the other is an even more ancient Sceptre! My rig is as follows:

Gigabyte GA-MA790FXT-UD5P
AMD Phenom II X4 955 Black Edition @ 3.2GHz
Corsair xms3 1333MHz CAS9 DDR3 8GB
Antec 900 Case
Cooler Master Hyper 212 CPU Cooler
2 DVD R/W
Western Digital HD (500GB/320GB)
Monitor: Dell 2005FPW
Logitech Wingman Extreme
Logitech 900 WebCam
Logitech Cordless Mouse
Soundblaster Audigy 2zs
5.1 Altec Lansing Speakers
D-Link DIR-655 Router
Windows Home Premium X64bit
EVGA 01G-P3-1158-TR GeForce GTS 250 1GB 256-bit DDR3
EVGA 512-P3-N872-AR GeForce 9800 GTX/GTX+ 512MB 256-bit DDR3
 

happaflapp

Allow me to qualify the performance of my 9800 GTX+ with BF:BC2.  This is with a pair of EVGA 9800 GTX+'es in SLi with a overclocked Phenom 9850 X4 @ 2800 GHz (soon to be a Phenom II X4 940 Black Edition), 4 gigs of XMS DDR2 RAM, and Vista x64.  Don't try to throw a 9800 GTX at a dual core CPU and expect great things with that game...it simply doesn't do well.

 
I couldn't disagree more. I had a pair of 9800 GTX+ in sli with a Core2Duo E8400 @ stock speeds and I was easily getting 50 to 60 FPS in BC2. Settings were all max and AF was 16x and AA was 16x @1920x1080.