The comparison between Boston and Philadelphia reminds me of software user interface design. In this case, Boston corresponds to the flexible design technologies: Flash, Flex, WPF, Silverlight, and so on. Philadelphia corresponds to the Windows and Macintosh user interface standards, which dictate the order and location of certain menus, the assignment of certain keys and combinations, the use of rectangular windows with rounded corners, the location and meaning of the controls for the window frame, and so on.
It's all very well to be really creative and "think outside the box" (gag) if what you're designing is intended to be a puzzle: a good example of that is J.K. Rowling's home page. On the other hand, creativity for its own sake just confuses users. I can think of dozens, perhaps hundreds of examples of user interfaces done badly for the simple reason that the designer decided that it would be cooler to have some spiffy art and effects than to follow any standards.
What do you think? Is there an ideal user interface? Can you think of examples of user interfaces done well that demonstrate balance between creativity and standards? What are your three favorites and three least favorites?