I've used both lounges for domestic and usually find the lounge by security to be the less crowded of the two. One can always stop there first and if it is extremely crowded, zip out the door and go to the other.

For EXP or OW Emerald on international itineraries, remember the Flagship Lounge is available to you regardless of class of flight service, and it is located in the larger lounge complex next to security.

Of the domestic flagships, my favorite is JFK then LAX, followed by ORD and then the tiny first lounge in MIA pulling up last.