I use stackoverflow because the community has much more adults and people who program for a living on it, and I phrase my questions without using Hopscotch. For example, the last question I asked was about implementing elliptic curve primality testing in Hopscotch, which I’m certain wouldn’t get any answers here. And I phrased it not by saying I need to implement it in “Hopscotch” (Cause most people there don’t know what that is), but I said I need to implementing it using only these certain math tools, no strings, etc and just laid out the limits of Hopscotch. I got quite a few answers that way.
I’d say use SO for questions that require someone with specific knowledge of specific algorithms that you wouldn’t get on the forum.