By qualitatively different I mostly meant to point out that TMI and Fukushima were both LOC accidents at water moderated reactors, while Chernobyl was of a much more dangerous variety. This was motivated by the fact that the OP glossed over that important point, and now you have filled in even more of the blanks; thanks.
Yes, I just wanted to expand on how completely different these reactors and accidents were. Also, it was a minor point but LOC Accident (TMI) is different than a Station Black Out (Fukushima), these are defined accident scenarios in the design basis documents for the reactors.
