Originally Posted by Anandtech
If we focus on what is likely to be the target resolution of 1680x1050, the Radeon HD 4850 ties its direct competition, the GTS 250 512MB, the Radeon HD 4850 leads more often than it trails or looses. The 1GB GTS 250 does edge out the 4850 in one more benchmark, but it does cost $20 more and we haven't tested the 1GB 4850 which might make the difference.
We've recommended the 4850 over the 9800 GTX+ in the past, and we'll continue to do so now that it's called the GTS 250. But the extra memory does help out, especially if the card is to be used for 1920x1200 on a budget (or maybe with an HDTV).
Power consumption is an advantage the GTS 250 1GB holds. The new board design is only required on the 1GB model, and board vendors may opt for the new design on their 512MB parts, but they may also stick with their current 9800 GTX+ designs. We expect that at first the 512MB GTS 250 will more closely resemble the 9800 GTX+. This does mean we are left with the oddity of the 1GB part drawing less power than the 512MB part for now. Once we get a 512MB version with the new board revision we'll have to take another look at power draw.
The GTS 250 1GB is a better option than it's 512MB brother, and it's also a better option than the 4850 based on our tests. It isn't a game changing difference, but its an edge nonetheless. Is the added performance worth the extra $20? That has to come down to the individual gamer.