Re: Glass and Reich. I think both have exhausted the stylistic territory they've pegged themselves into. Reich's "post-phase" works (most notably "Different Trains", "The Cave") are characterised by emulating speech patterns: this was grand breaking at the time, and as the burgeoning computer technology gave him more and more tools, he was able to produce something as sonically virtuosic as "Three Tales". Yet it was still old wine in increasingly slick bottles.
And it is not wine that has aged well -- Reich is very intent to throw Judaism in your face, not caring how off-puttingly smug he might come across. I for one is deeply repelled by "The Cave" and "Three Tales". By contrast, Glass is less likely to let extra-musical matters to influence his compositions. Even though his crafts are now old and derivative, there is still a reassuring quality, a certain "luminosity" that invites rather than imposes. In short, Glass is a seducer; Reich (at least late Reich) is a preacher.
Re: LugBug1's question about who pioneered "minimalism": probably La Monte Young, in particular his "String Trio" of 1958.
Edited by FalconP - 6/22/11 at 8:55pm