"MC-808 has motorized faders. No matter what pattern is called up, the faders will snap to the proper position. As a result, the parameter values and position of the faders always correspond, allowing the performer to see the values instantly and make changes directly. No more unexpected jumps in values when a fader is grabbed in mid-performance. It’s always in the right position." quoted from live sound PA systems
That kind of feature is important especially for live applications. The mc 909 has a better sceen but half the polyphony as well at 64 voices. the 808 has 124 voices. The sample rate on both of them is equal and they both have USB ports for direct link to your comp!!
as for the sample editing that the 909 has internal editing .....you can do this as well with the 808 via a software editor that comes with it. Plus the 808 is a few hundred dollars less so it makes this an easier decision!! For me its a polyphony and the motorized faders!
The thing is though if you can get a 909 for 750 USD then do it as long as it work properly. Good luck!
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