You are asking me a rather difficult question here. The Mojo and the CMA600i are very different animals. It is like you asked me to compare a mouse to an elephant. Well, both are mammals. In our case both devices are used to reproduce music.
As Relic has just said, the overall performance of a device depends on many things. The DAC section is just one piece of a chain. There is tuning and implementation, etc.
The Mojo as a DAC is slightly superior to the DAC setion of the CMA600i, if I had to put it into numbers, I would say 10-15% better. When I say better, I mean it offers slightly better depth and separation, all the well-known strengths of Chord DACs.
On the other hand the amp section, implementation etc makes the CMA600i a much better, more pleasing sounding device. In certain things you might loose 10% compared to the Mojo, but in other things you gain 60-80%.
If we made a list of ten sound attributes, I would say Mojo wins in 2-3 while the 600i wins in 7-8. It is hard to explain without auditioning, and there is personal preference too.
While you might loose 10% of depth and instrument separation, you gain so much on other things (bass/treble extension, body, texture, soundstage, balance, smoothness etc) that it is not really a competition and you won't mind loosing that 10% in depth for example when you gain so much with a high-end refined sound.
I hope this gibberish makes some sense to you.