Agreed, let's stop with all the "give peace a chance posts".
Comparisons between two multi-platform titles is healthy for the industry. If developers know we care and pay attention to the differences, they will make sure to spend the resources to make the platforms great on either platform. If no one cared that a game looked worse on the 360 or the PS3, I guarantee you that developers would not have gone through such great lengths to make CoD4, DMC and now GTA IV nearly equal on both platforms. Surprise: Madden 09 will now run at 60 fps on the PS3.
With talented developers any differences between the two versions will likely result from the minute differences between the two systems. For example, in GTA IV's case, my guess is that the bulk of the slight differences in the PS3 version are due to the mandatory HDD install.