Definitely agree that case-by-case should be the way to go, I can only say normally I'm happier (where an appreciable difference exists) with the newer versions based on past experience. An exception to that off the top of my head would be 'The Wolfman' Director's Cut where I think the theatrical version is punchier even as it loses a nice scene with Max Von Sydow.
But that isn't an important or notable film!
But then, as you point out it's also worth bearing in mind when a Director's Cut IS actually the work of the director coming back themselves to rework the film perhaps as they originally wanted to and not where the studio just goes in and makes such additions themselves without considering how to put things back in yet markets it as a DC. I'm obviously also not necessarily talking about the recent emergence of 'unrated' cuts which are proliferating especially in the horror/sci-fi genre because those are just cash ins for the home market I find that just add more gore etc
I'm talking about your 'Aliens: SE', 'The Abyss: SE' and your Ridley Scott stuff and even the likes of Robert Wise's work on TMP.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist