Now here's what I have noticed. With both the Dreamwear full face and Airtouch I breathe mostly through my mouth. This of course causes dryness and all sorts of other issues. At the same time I like the lack of pressure on my nostrils. However, I don't get as good a sleep with those masks.
I tried the Dreamwear nasal, expecting to have lots of problems with mouth breathing. But surprisingly, I have had very little of that. Looking at my sleepyhead data perhaps once a night, and usually pretty close to waking up time. Even weirder, I know I have kept my mouth open. I can even drink water without air blowing out my mouth. The big difference I have noticed though is that using the nasal mask my nasal passages clear up, whereas with the full face mask, they clog up quickly.
My theory is that with the nasal mask, the air pressure works to open the nasal passages to the throat, while pressing the soft palate forward and blocking off my mouth. While with a full face mask the opposite happens, pressing the soft palate back blocking off my nasal passages.
Assuming this hypothesis is correct, which is a better situation? So far none of the masks are really to my liking. I am a stomach sleeper. The Dreamwear full face is just too small and leaks, the AirTough puts far too much pressure on my nasal bridge and protrudes too much so that I can turn on my side, plus the air hose gets in the way, while the Dreamwear nasal presses up on my nose, being painful and always dislodges when I turn my head on the side. Since there really is no place to try on masks, and my provider isn't the most helpful, I need to really research my next mask.