What's the difference in range between Airport Express and Extreme?
The Wireless specs are the same.

The Features of each one, however, are not. Here's a few differences:


Packaging (obviously)
USB connection: On Express, only printers work. On Extreme, Printers and External HDDs.
Airport Extreme is able to create two wireless networks (one regular, one guest). Apple site states it has a guest network.
Airport Express has a P2 connector for AirPlay audio.