The panorama shots are available in two resolutions - "Detailed" and "Standard." Both cover the same area and are the same dimensions.  The "Detailed" image has a much larger resolution. You can zoom up to 250% and still have plenty of detail!  The "Standard" image is much lower in resolution, and can't zoom past 125% without suffering loss of detail.

Image sizes are given next to each description.  These are QuickTime Panoramas.