Hal 9000 said:
I've never actually seen the theatrical versions, to be honest. I became a fan just a year or so ago.

What are the differences between the two versions when they enter Lorien?

The theatrical continues the scene after Haldir saying "The dwarf breathes so loud we could have shot him in the dark". Aragorn greet Haldir in elvish, and Gimli says that the woods are perilous, and they should go back, to which Haldir replies "You have entered the realm of the Lady of the Wood. You cannot go back. Come; she is waiting." Cut to the fellowship ascending the stair of Caras Galadhon.

The EE version is better in many ways, but they should have reshot it with the updated costumes. As it stands, it really sticks out as a scene that was never meant to be in the movie.