Well for us new players that waited after launch for the server to become playable in lowbie areas that haven't even been able to log into Elysium and create a character to play. The choice is pretty simple.
But in the end im probably gonna pick the server with less population. If many switch server i might pick elysium later. Blizzards retail vanilla servers held max 2500 players before you got a que. The game just wasn't designed to host over 5000 players and give a good gaming experience. They could launch 3-4 new servers tomorrow and they would probably still have more players then needed for a healthy population on all their servers.