Barry,
A agree with your assessment of B9th:IV. But I would not go as far as B9th:1-III is greater than Mahler Ninth. They are both GREAT works but one isn't superior to the other.
I am not enthusiastic about Rattle's performance either. I mean, it's not bad but it's not special either. EMI created one of the worst sounds from the Berlin Philharmonie Hall: opaque, murky and of low resolution lacking details.
That said, I like Kurt Eichhorn's recording of the complete B9th. Not only Eichhorn does far better a job than Rattle, the version he used is better than the one used in the EMI recording.
John,