One major down side with UA is the upcoming changes on earning miles, especially for regular members, whereas the number of miles earned is based on the cost of the ticket (at least on UA metal, it's unclear how this scheme is applied to partner tickets).
LAX
The UA website does state the following in regards to the new 2015 program.
This new way of earning award miles will apply to most tickets for flights operated by United and United Express. It will also apply to tickets for flights operated by a Star Alliance™ or MileagePlus partner airline when the ticket number starts with "016."
Tickets for flights operated by a Star Alliance™ or MileagePlus partner airline that aren’t issued by United (ticket numbers that don’t start with “016”) will still earn award miles based on distance flown and the purchased fare class.
So in order to earn the actual flight miles, you'll have to book direct with the partner airline and credit mileage to UA instead according to UA's mileage accrual chart with partner airlines.