I’d read over this black tie guide. Make of it what you will. I tend to agree with the article’s analysis of deciphering the invitation.
Generally speaking, if I were invited to a black tie event, then I would wear a tuxedo regardless if the invite said “requested”, “recommended”, etc. Ultimately, it’s going to be your call to make.
In regards to black suits, I tend to think they fall short of black tie in many ways. They lack the grosgrain lapels, often have notched lapels, and two button fronts. It strikes me as funeral attire — or like you’re in a Tarantino film. Perhaps it’d be passable in a pinch, however, it won’t have the elegance of a tuxedo for the situation.