The CC121 does ALMOST everything the full range of the CMC series does, give or take.
It has a control mode, of being able to use all the EQ pots on the CC121 in Quck COntrol Mode…It does all transport controls, has a great quality fader (apllicable for every channel you select) Its got the majority of features of the cmc series, apart from the Pad control, and layer switching…also the CC121 is fixed in as much as what you see is whats asssigned, with the CMC series you can assign things to suit your needs…
If you want a great controller for Cubase, buy the Cc121, and add on what you would use the most. (ie, more rotaries, or need Drum pads etc…