looks like this is a common question. i would say though that there is no comparison between the two though, especially if you have plans to expand.
the sequencer on the rm1x is not only far superior to the mc range but if you want to run other hardware from your machine then it blows it away. drum sounds are weak on the old rm1x though.
i produce techno and use the rm1x at the centre of my studio. i find the features on the sequencer are plenty.
i run a drumstation from it along with a few synths and run a midi controller into it. it works a treat.
look at www.rm1x.co.uk which is a pretty good site for owners.
if you only want to use the box as a stand alone unit then the case is not so clear cut maybe.