I was born an bred an "Eastie," but since I live out West and have flown the West side a few times now since the merger, I must say that I am struck by two big differences:

1) Service on the West side seems to be more consistent.
2) Maybe I've just been lucky, or maybe it's just the desert heat, but the East side seems to be plagued with far more operational issues - even in perfect weather. I don't experience drama when flying on West itins the way I do flying on East itins.