I think it's valuable that many of us have these different approaches to what we appreciate about a performance. Not even just of Mahler's music, but in general. It goes to show how many different angles music and art can be approached from, and that it means something different to everyone. Vänskä's Mahler is by no means my favorite; I prefer the likes of Chailly, Stenz, Bertini, Bernstein, Blomstedt, among others. However, what I do appreciate about Vänskä's Mahler is akin to walking around in an exhibit of sketches that were traced flawlessly: "well, you certainly drew it as correctly as possible. Looks just like it should! Good job, Mr. Vänskä." Vänskä's M6 is a "perfect tracing," whereas Bernstein's DG M6 is an entire painting: slightly flawed but fully human. But again, it just depends on what you're in the mood for.
And I definitely agree with you when you say that Vänskä does not offer a transformative experience; I would turn to at least 10 other conductors before him for that kind of listening.
I like what you said about different approaches with an overall cohesive purpose. It's funny, given our generally different approaches to listening to recordings I couldn't agree more with the examples you gave.
Also PS. I want to clarify that Vänskä's Adagietto is not entirely my cup of tea either; I was just saying that I do personally find passion in it. My type of approach to that movement is more along the lines of Chailly, Abbado/Lucerne, Shipway (even though it's slow), Gielen, the Fischers, and Harding. I figured I ought to say this before I get ripped to shreds on this board.