Turisu said:
I hope you reconsider the special edition; the extra scenes kill the perfect pacing of the film and the theatrical version is Cameron's original director's cut since he had final cut of the movie on release.

Actually, for Aliens, the Special edition is Cameron's director's cut. He prefers that cut of the film and the studio forcibly created the theatrical cut. (Of course it's up to you what cut you prefer.)

In the case of Alien, the theatrical cut is the director's final cut, and the so called "director's cut" is just an alternate cut Ridley Scott did for the dvd.