To answer this question, I just conducted extensive testing in my lab (i.e. I spent 20 minutes playing with it again on my couch). Here is the definitive word on the matter.
Basically, the other modes sound slightly compressed to me, albeit in somewhat different ways. Bear in mind, they all sound great. But there is a wow factor when I return to normal mode. There is just more to hear. I'm a classical music guy, so the difference comes across as more vividness to each instrument, more information about resonances of the room where the performance took place, more of a sense of the placement of the mics, stuff like that. It just sounds a bit more saturated with information. The other modes sound great, but normal mode sounds uncanny. It's much more evident to me on my full-size headphones (Shure SRH1840) than on my IEMs (BLON BL-03). My assumption is that the other modes manipulate the data stream in some way and so they introduce the potential for some degradation.
The differences are small, so naturally, I would be amused by a fierce and emotional debate on this topic.
