Clearly you guys aren't thinking about the situation. Obviously if they are the same resolution it makes no difference, but as far as I've known, if you think about the system being a computer, which it is, and not a console this makes perfect sense. If the computer can't display the picture in accordance with the specifications of the game, which in this case the game has the issues, then you would essentially have to drop the resolution, or picture size, to lessen the pixels per inch so as to minimize the work of the computer. Stop and think for a second and maybe you'd understand the concept if you knew what you were talking about when it came to computers. I've got two degrees in this subject so try not to fight so hard guys.
Your two degrees don't disprove the point. Simply lowering the screen size does not lower the resolution and therefore doesn't reduce the load on the PS3's GPU. Hooking up my laptop, for example, to my 32" TV doesn't automatically yield differing performance from just playing on the laptop's far smaller screen. The outputted resolution remains the same therefore the performance remains the same.
What if you lower the resolution from 720p to 480p?
We can't do that with PS3s. No matter what the display device is, even if it's an SDTV, the PS3 is attempting to output at the same resolution developers set their game to... whether it has a tangible benefit or not.