Pam's right, it's prettier. Another stance is that right now we have a growing user base and must keep in mind that they desire to upload more. Shortly, having a thumbnail picture extracted adds 30% more size to each shot, as that must also be processed for every single shot on the gallery. Instead, I'd rather have one standard which is also the standard used on the guide for a wide shot. 660 pixels is relatively small.
In this case, the disk space usage is more important than the bandwidth consumed. I know this is a thread that has been inactive a bit but gallery applications keep coming and I wanted to provide my input on the matter.