Both do the same thing —
AirServer: allows you to receive AirPlay feeds, similar to an Apple TV, so you can stream content or Mirror your display from your iOS devices or Mountain Lion.
Reflector: Wirelessly mirror your iPad, iPhone or iPod Touch screen to any Mac or PC.
There are some minor differences. For example, Reflector allows one to show a moc-device frame of either black or white while AirServer does not. AirServer can be installed on five devices per license, while Reflector can only be installed on one.
If you’d like to try AirServer, use this link for a seven day trial and I’ll get an additional 3 days tacked on to my trial.
If you’d like to try Reflector, the trial version only runs for 10 minutes.
Let me know which one you prefer!