From the Hood quote it certainly looks as though it's altered enough (and both versions were successful enough) for each to have a separate article - that's one issue. (Although I do wonder about the 1983 Sadler's Wells version. If it had a new book and lyrics, it clearly wasn't Hood and Ross's version - so is it a version of Count, or of Graf? Does anyone know about the music?)

As for the other - I'd say it's definitely an operetta. Unless we can prove some substantial alteration of the music - style, vocal range, whatnot - it's the music from an operetta, and the show is an operetta.

On an unrelated note, doesn't anyone who's already worked on this article know how the plot resolves? "Things work out okay and there's pretty music" isn't quote what one hopes to get out of a synopsis.