Black tie is the top of the Western formal scale, and it usually signals a serious evening: a formal dinner, a five-star reception, or a wedding aiming at the grandeur of a European occasion. For men it means a dinner suit with the right accessories. Not a dark suit. Not a bandhgala with a bow tie added. And not a black suit worn with a black tie, which is the most common misreading of the phrase and the easiest one to avoid.
What black tie actually asks for
A dinner jacket in black or midnight navy, dress trousers with a silk stripe down the outer seam, a white dress shirt with a pleated or piqué front, a black silk bow tie you tie yourself, and black formal shoes, Oxford or opera pump. The whole thing is specific. Swap in a dark suit or an ordinary shirt and everyone who knows the code reads it as a decision rather than an accident.
Black tie is some of the most exacting work we do. The dinner jacket has its own construction: the way the shawl or peak lapel is faced in silk, the trouser waistband and stripe, the button treatment, the finishing at the buttonhole. Those details are what separate a dinner jacket from a very dark suit, and they're why a good one still looks right twenty years and a dozen dinners later.
The black bandhgala, and when it works
At an Indian black tie event, a fine bandhgala in black or midnight navy in good suiting cloth is a fully accepted alternative to the tuxedo. The stand collar does the job the tuxedo's closure does: it signals that you've gone as formal as your tradition goes. A fully canvassed black bandhgala with silk-covered buttons and a precise fit reads as Indian black tie in any room in this country.
The caveat is that it's specifically an Indian convention. It wouldn't pass at a black tie dinner in London, but it's entirely correct at a wedding in Chennai or Delhi. If you're choosing between the two, the honest basis is which one you'll wear more comfortably and which one looks more like you, because both of them are right. One thing to get right either way: whatever you choose has to be made to fit you, because both the tuxedo and the black bandhgala live or die on the shoulder line and on the closure sitting flat.