Nick the synth sounds are really good in the MZX. That's certainly do to the Hex Layer feature. I'd give the edge to the MOXF-6.., However, it's not to say that the MZX can't compete with it (because I strongly believe it can). IMO what you'll see (hear) is that I think Yamaha has more experienced sound editors on their staff.

The MZX can produce some amazingly large sounds, but I think Casio's resources (in terms of highly skilled techs) is why Yamaha takes the edge there. Don't get me wrong.., some of the Hex Tones are really good. The tools are all there as well. Not only that.., there are synth bases that have their own dedicated "Base Synth" that's utilizes the Hex Layer Feature.