Behold! I have indisputable proof that the web interface for MobileMe is going to change.
Why are they different? Because Apple has updated Mail, Calendar, and Find My iPhone in the past year. They haven’t updated Contacts, Gallery, or iDisk. There is no way that Apple would let this discrepancy continue indefinitely; they are too obsessive about UI. The only reason they would allow this is because updates for the other sections are in the works.