Why would I want lame over the encoder the central uses now ?

LAME is an ongoing project where they keep tweaking it to get the best possible sound quality out of it. So, in theory, a very new copy of LAME could sound better at a given bitrate than an old copy of the Fraunhofer encoder.

However, at 256kbps, I can't tell the difference between the original CD and a Central-encoded file, let alone being able to tell the difference between LAME and Fraunhofer. So at that bitrate, I have no real need for LAME.