I work in Pomona, and there is a school near my office called Western University that has planted a few M. Alba and some Champaca! The Alba is blooming like crazy right now. I just may put mine in the ground since theirs looks so good.
2 of the ALBA's have seed pods. Are they worth it?
Of course, give it a go (I believe the seeds are mature once the pods start to turn brownish). Correct me if I'm wrong, but there could be a possibility for slight genetic variation with the seedlings and they may end up being better or worse in some aspects. They are notoriously difficult to root and are mainly propagated by air-layering or grafting on seedling stock of Michelia champaca.
It is said that there is only one type of Michelia x alba out there that resulted from a hybrid from a very long time ago in Asia. And all Michelia x alba are from vegatative propagation of this origin. But from what I gather, I believe there could be several varations of Michelia x alba that exists out there, mainly in respect to the flower size.
In Thailand there is a very small flowered form called 'Chiu' meaning miniature; it is still unclassified. Whether it is a new species or hybrid or a selection...