In 2011, I'd go UA. Their route map is far larger than US and even though they're alliance partners, things are always a little better on your "native" metal.

UA has low fees on awards, flexible one-ways, and E+. And when US craters (which I think it eventually will), there's a decent chance that regulators might allow AA to absorb it, not UA. So that could throw your stash in the direction of Oneworld, not *A.

Only "pros" for US are reduced award levels for CC holders and apparently less Starnet blocking.

Last week, four of us flew MCI-YVR (with connections), 2 on US roundtrip and 2 on UA/AA, one-way on each. The UA and AA segments all performed fine. Both US directions where canceled due to "aircraft availability". (No real weather issues anywhere.) And at the airports, the US people were disorganized and unhelpful. We weren't auto-confirmed on later flights the way UA and AA do. We couldn't even use a kiosk to rebook. We had to find humans to talk to, which was a challenge. Simple tickets, US metal, ticketed by US. It just seems that operationally-speaking, this is a dying company. I know it's just one experience but I've always felt like UA handled irrops in general better. Overall, it seems like a more robust company better able to adapt to day-to-day challenges of running an airline.

I know I would never want to fly US regularly, even with top-tier status. UA as a 1K was fantastic and UA as a lower elite is still not bad.