I have wireless n on my MacBook so I was looking to get a wireless n router. What can the airport extreme do that the express can't do? Would I be able to use the express for a home network with three computers and get n speed?
Now on to the good one. The airport extreme is just more functional. It will allow you to plug the computers in directly to receive gigabit speeds, which are much higher than wireless n speeds. The AEBS also allows you to plug in external harddrives to the usb port, so all of you computers could share the same external harddrives. The express only allows you to share a printer, the AEBS's USB port can also be used to share a printer. All in All the AEBS just has more functionality.
The AirPort Express will handle N speeds on multiple computers just fine, as long as all computers have N capability. Also the AirPort Express allows you to wirelessly stream iTunes music to your stereo speakers, which the AirPort Extreme can't do.