The MC-505 was built in the mid 90´s so the sounds are more Acid like and the soundchip is a bit more oldschool than the 2002 built 909. None the less, both machines fit together perfectly because the 505 has features that the 909 does´nt.

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 synthsounds are so clear that I can almost look right through them
The MC-909 is very easy to handel and pattern building is super simple.

for specific questions, just PM me

Informative. Thanks for sharing.

I am finally learning my MC505 and I must say, both the Portamento and Groove quantize are two things I tend to use a lot! The machine is super intuitive and I haven't even looked in my manual yet, I am guessing the 909 is no different.

I'd love to try an mc909 someday, but I am sure it is at least as much fun as the mc505. Probably even better because of the build-in sampler.