That said, how many here are carrying the revolver because of it's ECQB advantages over an auto or simply because it is more convenient and comfortable?
A little bit of both for me. A snub revolver has some definite advantages over a semi-auto.
As to the ammo capacity issue, you ultimately have to go with what you're comfortable with. But I consider capacity/speed of reload down on the list of priorities. Claude Werner has done a a couple of studies of civilian self defense shootings and, IIRC, none of the 400+ he examined involved a reload, with the vast majority being resolved in 2-3 rounds. Gregg Ellifritz's study similarly showed that, regardless of caliber, most incidents required 2-3 rounds. Even Massad Ayoob has said that of all the shootings he's studied, when reloads were done they had little, if any, impact on the outcome. Have their been situations where more rounds were fired? Sure. I can think of a couple off the top of my head that went 20+ rounds fired, one of which involved a .45ACP Glock. But those are extreme outliers and the people involved had tactics and/or luck on their side.
In the event of multiple attackers, nearly all of the videos I've seen of actual self defense encounters showed the assailants fleeing as soon as their intended victim started shooting. In the unlikely event that multiple attackers continue their attack, it then becomes a matter of running out of time before running out of ammo.
Add that to a snub's other attributes, including ECQC advantages (you can check out Michael deBethencourt's blog and Ed Lovette's
The Snubby Revolver for more info there) and the higher likelihood of carrying it over a bigger, heavier gun for some people, and the snub revolver becomes a good solution for many people.
Are snubs for everyone? No. I certainly have no issue with someone choosing something like a Glock 19 over a snub if that suits their situation better, whether it's the result of a well thought-out risk assessment or just the comfort of having more ammo. Someone may be willing to carry a bigger gun because they shoot it better, which is a valid reason. Snubs and semi-autos each have their own strengths and weaknesses, and you have to decide which would work better for you.
Given my current situation, I'm comfortable with a 642. I know how to run a revolver, I can shoot it well, it's easy to carry (IWB or, rarely for me, pocket carry), it's reliable, it's reasonably powerful (my carry load, Speer 135gr SB-GDHP +P, has a proven track record in actual shootings), and I have contingency responses planned if it proves to be insufficient because I'm aware of its limitations.
At the same time, I haven't ruled out getting a compact single- or double-stack 9mm as a carry option.