It depends on the culture of the firm you're interviewing at. There exist many companies at our industry where a suit does not communicate something desirable

It depends on the culture of the firm you're interviewing at. There exist many companies at our industry where a suit does not communicate something desirable about you. For them, I'd go in my Sunday best rather than formal attire. For men I think this is approximately "Khakis and a long-sleeved shirt, ironed." If you're in doubt about this, ask ahead of the interview. "Hey Bob, quick question since you'd know better than me: are you guys a suit-at-the-interview sort of shop?"