1 gb 4850 or 512 mb 4870?

The DDR5 would be better, but why aren't you just getting a 1 GB version of the XFX 4870? There is one on newegg cheaper then that one.

Edit:

Here it is.

http://www.newegg.com/Product/Prod [...] _-14150394

There is even a combo deal where you get a free game. Don't like the game much myself but free game nonetheless.

really comes down to resolution of your screen and what kind of games your planning to play. There is quiet a bit of difference when you add up the higher clock speeds and the DDR5 but if your playing on a small res then the 4850 will hold it's own quiet well.

I would say spend the extra cash and get some more power in case you want to move up to a bigger screen later on or you want to play something like Crysis or Far Cry 2.

A world of difference for $30. No brainer, go for the 4870 1gb or even the 512MB. I have had both a 1GB 4850 and a 512MB 4870, and the 4870 really showed a big difference. If youre playing at lower than 1650x1080, the 512MB version should be perfectly fine.

If you are looking for cheap, and 1 gig of memory, here you go.
http://www.newegg.com/Product/Prod [...] 6814129117
If you want a fast card that is well worth every single penny you pay, get the 4870 1 gig. You can't buy a frigging half tank of gas for $30. If you cannot afford that, you need to either stop gaming or find a job.