Functionally, in conversation they’re the same. But, that said, if I was talking about somebody the listener was close to, I’d use “had died”, rather than “is dead”.

Why? Because it’s slightly less direct, and I’m British so that’s the path we take.

Pointing out that someone “is dead” directly alludes to them being a corpse right now. Saying that they “had died” merely references something that they did.