I prefer ORD mostly since you simply exit and turn left or right as appropriate to get to your UA departure gate in C. Literally a minute or two away. Can cut your waiting at the UA gate down to nothing, and maximize your lounge time since you don't have to worry about an elevator, or a long hike. Having said that, it is slight hike back through the tunnel to the LH departure gate in concourse B, or waaaay over to Term 5 for any of the other *A carriers if those are your flights. LAX and SFO are tied for second, IAH is nice but I always seem to hit the crowded times. I loathe everything about EWR and have only visited the PL lounge there once. Nice lounge, but still its at EWR.