Lemmon
HH lets you combine, useful if one of you generates status, but minorly costly as you only have one account to update quarterly to get the bonus points

Mikey
You can travel "together" on separate carriers/flights to many of the same locations! But it seems to me that people making the commitment to marry should be flexible enough to be together when they vacation regardless of the carrier. If she flies that much on AA (100,000's) and hates UA ("0"), what is her basis of experience on UA to judge her hatred?