Most games are not optimized for more than 2-4 cores. So, if the 255 has 2 cores that are faster in GHz than 2 cores on the 6 cores, and the games is using only 2 cores, then yes, the X2 will be faster. Maybe not by a large margin, or with every games, but having extra cores that are unused don't really helps gaming.
Where I live, I can get a phenom x4 965 3.4 GHz for 90$ and the 1045T at 2.7 GHz for 99$. Of the 2, the 965 will game much better than the 6 cores, and by a wide margin.