It uses the map from TBOGT, so all the night clubs are on the map and you can hear the music from inside, people queuing up, etc. Rotterdam Tower is complete, so even Johnny can climb right up to the top like Luis, also you can use Luis's parking space in TLAD so you have more space for parking. There have been slight changes to handling, I've been told some bikes have been improved, up to now the only one I've tried is the Lycan and it turns easier and quicker in EFLC compared to DLC. Small cosmetic changes, textures look less compressed, most evident on Johnny's jacket.
Another person over at GTAForums has said the club has been changed slightly and now has Lights at night and is lit better and more dynamically inside, haven't had a chance to test this as my save is a completed file. The guy also said the animations are different, which they are, but really not that much different, and that Cutscenes have been altered, which again I can't verify as my save is a finished game.