I too have found that what is the most comfortable to wear is the least concealing, while what is the most uncomfortable provides the most concealment. For me, the most comfortable and supportive bras are under-wire. I'm a 40D and still growing. For me, while I don't wish to draw attention to myself, I do want to be comfortable. Going bra-less just isn't comfortable most of the time because of the sweat under my breasts and the constant distraction of motion. Of course, winter is always easier because I can hide under lots of clothing. Summer can be tough as it often leaves nowhere to hide. I've yet to find a sports bra that I could wear for more than a short time.
It's true that most of the younger guys here (perhaps 40-ish and below), are far more concerned about their physical appearance to others than us older guys. I see some posts from guys that appear to have little more than hard nipples who are "freaked-out" and want immediate surgery. My point here is that for many younger guys their sense of self is closely tied to their physical appearance. Older guys (in general) have come to understand that their bodies are just containers for the person that's inside. These containers are hard-wired to self-destruct. That is, your body will do all sorts of things to you without asking your permission. Growing breasts is just one possibility. Tumors, cancer, heart disease, aneurysms, strokes, blindness, and a whole host of other ailments are on the list of things your body may do as well. Many of us older guys (and some younger ones) have faced a few of these other things along the way. In doing so we learn some lessons about perspective that provide a clarity we didn't when we were young. My breasts are a result of hormone deficiency and the side-effects of various medications. My other health concerns are of far greater importance than my breasts.
Good on you for keeping your head straight on this. Many guys aren't able to, even many old guys. I had known a guy for over 35-years who just couldn't handle the fact that I have breasts and wear a bra. He proved the truth of the saying that your friends are the one's coming in the door when everyone else is going out!