The movie makes the plot more understandable, but leaves out a lot of good stuff.
Do you mean it makes it more understandable simply by virtue of condensing it, or does it actually add/change content? Just curious.
By condensing it. Like I said, my first watch of the series had long gaps between the disk sets being issued, so it was easy to lose track of what was going on. Even rewatching it one-ep-per-day, my limited attention span was a bit challenged (my problem, not the anime's).