MileagePlus Vs Club Vs CSP...
There's a calculator here that will let you see which earns the most points.
http://milecards.com/3845/calculate-how-much-united-mileage-plus-club-card-earning-power-stacks-up/
If you spend $25k on the nose the Explorer earns 1.4 miles per $ due to the 10k mile threshold bonus.