The MEGAMix function.
The Portamento knob.
The Groove knob.
The ability to control the individual amount of delay assigned to each part.
The Ad-Lib function from the D-Beam.
Most MC-909 users agree that both machines are different enough to justify keeping both of them and integrate them using a MIDI cable.
just copied it outa Wikipwedia
The MC-909 has the TR-808/909 sounds that I have been looking for as a technohead
The MC-909 is very easy to handel and pattern building is super simple.
for specific questions, just PM me