The best location depends on how you and your business communicate best. If you have a strong brand presence, a compelling offer that is clear and easy to engage, then catching everyone as they enter the exhibition is a good move. The Entrance Lobby is a “Marmite” option, for some, it puts you in a place that everyone will pass on entering and leaving. For others, it’s a place where the visitors are distracted and “on their way” – in or out – and not a space where they loiter and talk.
The down side of being near the entrance is that if visitors are on a mission to go and see the exhibitors that they know are there and have arrange to see, then they will walk right past you.
You might feel that the best option is the area of the exhibition where people will be more relaxed, spend time, loiter and be in a receptive frame of mind. That is especially true if your approach is to building business relationships than driving final transactions and deal closure.