Theatrical is a solid version to watch and probably the right one. That said I own the Redux version since it had some additional content. Of course the way that it was placed into the film disrupts the flow a bit, but does fit in with the various messages and metaphors in the film. Also, the effect of those additional scenes makes the film a bit spookier and adds to the feeling of things progressing from reality towards insanity the closer they get to Kurtz. It's by no means a bad cut, just really, really long and definitely not something to watch on a whim. I can't truly speak about the Final Cut version since I haven't personally watched it, but I've heard that it's shorter, but still a more difficult watch than the Theatrical version.