Using different SSID means you've created separate wireless networks. That would not work for me since I would not be able to use devices connected to one network from the other. My printer is connected to the USB port on the AirPort Extreme so that everyone in the house can print. My Mac Mini serves as a music jukebox. I use the Apple Remote app on my iPod Touch to control AirTunes (the AirPort Express is connected to the home stereo) running on the Mac mini. I also use Simplify Media so that I can stream my playlist to my iPod Touch when I am working in the yard. None of that would be possible if I used different SSIDs.