I wear an RF1200 (had an RF1100 before that and, for a brief time before selling it, an Arai XD4). First off, I like the helmet and have been quiet happy with it overall. However, I don't consider the RF1200 "quiet" but I also wouldn't consider either of those other two quiet. I certainly would never consider riding with it without ear plugs but, to be fair, I'm in my mid 40's and have tinnitus from abusing my ears in my youth so I do what I can now to minimize any further damage including wearing ear plugs any time I ride. I do use a bluetooth system in it and can hear music or phone calls just fine with ear plugs in. At highway speeds it does get a bit harder to hear but I also try not to turn it up all the way.
As far as comfort, that's obviously going to be subjective but I find it very comfortable. I've done 500+ mile days with it and don't give the helmet any thought at all. Air flow is, in my opinion, pretty good. On a hot day I can feel the air moving through it. Having the vents open does make it noticeably louder but as noted above, I don't consider it quiet to begin with and opening the vents only makes it a little bit louder. The rear vents are sort of fiddly so I generally don't mess with them. Closing them didn't seem to make a significant difference as far as noise and having them open when it's hot makes a big difference.
I have both a dark smoke and a clear visor, both with pinlock lens, and when I'm out for more than a short ride I just bring both. It takes seconds to swap them. Definitely get the pinlock if you get one, works very well at reducing, if not eliminating, fogging on chilly mornings/days.
As a side note, up until recently I had an older Sena comms system in it and it fit very well including the speakers in the pockets. I recently replaced that with a Cardo Packtalk Slim and that does not fit nearly as well. It does fit but not well. In fact, I'm doing a week long trip next week and am not entirely sure that I won't have to tear it out to keep my ears from killing me after a long day.
2018 V-Strom 1000XT
2011 V-Strom 650A (Sold)
"Remember, you don't really own anything you can't carry at a dead run."