I have to say, MaNGOS does the job for me, Its been around for years and now has a very large community, easy to find when you stop hosting for a couple of years, easy compilation, install and configuration, easy modification and updating.
Constantly increasing support relatively stable.
but after saying what my favourite emulator, the emulator couldn't possibly be complete without the 2 side projects: Unified DB and Scriptdev 2
Both of which are fantastic and i love for all the same reasons as i love the mangos core :P