The radeon will be the equal to aproximately of the gtx+ Its also going to be cheaper at $150 after MIR or 170 before.
Three things to consider - the GTX+/Overclocked GTX have dual slot cooling - so unless you have adequate cooling in your case you have to consider the fact that the 4850 doesnt so another 120watts of heat inputted into your case.
The radeon 4850/4870 WILL be faster in the long term by a decent margin because as more direct x 10.1 games come out and it is mandatory to use direct x 10.1 in direct x 11 (which is coming out in a year) the 4850 will have a longer service life than the GTX+ also theres the fact that AMD has better memory management and the GTX can choke when it doesn't have enough memory.
The Radeon 4870 with the game grid is 250 after MIR or 270 before and it out performs both by quite a decent margin and comes with dual slot cooling and beats the gtx260 by a little margin now with more to come in the future when direct x 10.1 is better utilised.
Also the Radeons do AA better than the geforces as well.
Tease.
