The 123 minute version is my favorite because....
...it doesn't answer every question and put things into a nice, neat little box. This goes against 99% of all movies. The fact that things remain unanswered throughtout a lifetime makes the film much more powerful, and relatable to almost everyone watching. This is one of the few movies where the shorter version tells a better story by not telling the whole story.
Most movies with extended versions just add/extend certain scenes but don't change the plot of the film. This film does.