I'd be the first one to say a gentleman needs several suits, and I don't disagree that at the ends of the spectrum other suits would be better suitedtongue_sm) to specific tasks ... charcoal better than mid-grey at a funeral, seersucker or cream linen better at a July wedding, and so forth.
But the key here is "which suit will be on average best at all those uses?" I'll say that mid-grey is 'good enough' for a funeral, so long as you pair it with black tie/belt/shoes, and if you want to add a bit, a black arm band is traditional to demonstrate that one is in mourning.
Well, wool ain't always wool, if you know what I mean. A heavy flannel or the like is going to wear a lot hotter than a lightweight wool ... "tropical weight" wool is very light, and you can get high-twist-loose-weave wool that is very good for having the breeze blow through it.
My main gripe with dark suits, be they black, navy or charcoal, is that they are the wrong colour for summer: wearing dark clothes in the sun is a surefire way to turn yourself into a solar energy pannel ... yuck. (Heck, I once made the mistake of buying a black linen jacket ... even though it was unlined ... it was an oven!!)
Any suit that I've ever worn in the summer has become an oven. However, pit stains in a dark suit don't look nearly as ridiculous as those in a light colored suit
