I live in the LA area & do both UA & US. US usually prices out when flying to the eastern part of the USA from the west coast. I take UA (or others when long hauls are under $100 or so--example, LAX-MIA for $97.50! on CO) when I can't get US to price out decently. It takes only 25K to get systemwides from US and at 50K on US, you get 100% bonus on miles. Say you want to go to LA from SEA, the best way is with UA. Best of success whatever decision you make!