What about the EQDs? Would you easily spend $6K on UA to get gold with those 50K miles? With AS/VX (it's VX btw) there is no minimum spend and you can qualify for gold with 40K miles on only AS/VX. And, you'll earn more RDMs on AS/VX as well (double actual miles flown for golds on most economy fares).
You can still collect UA miles and book *A awards without flying through CC spend.
If schedule is really important, UA is better.