well i went for the athlon x2 for a few reasons, one i didnt want socket 940, becuase its support is decreasing, and the motherboards are expensive. socket 939 opterons are only "recommended" for a tyan motherboard from amd's website, so i didnt want to buy the opteron and end up putting it on a motherboard which would not support it officialy in its drivers and such. finally the two cores are very similar, and the athlon x2 is cheaper.
