How many threads have you posted this same question in? I think I came across 4 or 5.
BOM has more facilities but is the largest of the 3 airports so you might have to do a lot of walking.
HYD would be the smallest & with recent renovations I wouldn't know what the situation is with lounges, facilities, etc.
BLR would be convenient in terms of the shortest flying time to SIN. I have only connected international to international once here & it wasn't the most pleasant experience.