My favorite changes from the stage........
Keep in mind, i've never actually seen the musical on stage, so maybe im not the best judge, but ive read enough about it to know some of the big differences.
I mean sure, the dubbed singing is different from live stage singing, less personal blah blah blah etc....
The changes i noticed, however, deal with the overall musicality. For example, changing the Overture to include Maria and not Somewhere was a nice change, amping up the Prologue score by a little more emphasis on percussion, as well as integrating the Procession and Nightmare from the stage to make the scene overall more chaotic. Also, extending the Mambo trumpet solo was a nice touch, and is actually my favorite iteration of the piece.
But my most favorite change was changing the key of Maria from Eb to Db. Given that West Side Story is very much a Romeo and Juliet-inspired, i always felt Maria should have a little bit of sadness to it, and, IMO, Eb can't convey that as well as the key of Db.
Granted, these are conceivably small changes compared to the song order of Krupke/Cool and America's lyrics, but the orchestral changes here and there are what stuck out to me the most.