Few more UA points:
- once you make 1K/GS on UA you'll be pulling in more RDM than you will know what to do with
- Polaris lounge at SFO is better than what CX has to offer @ SFO, although both airports have a Centurion lounge
- UA SFO-BOS flights are all lie-flat and non stop which neither AS nor AA offer.
Someone else alluded to this, if there is a way for you company to use PassPlus (i.e. essentially buying a $50K UA gift card) you'll be GS off the bat.