In addition to these and what you replied to, there is also the ability to downgrade the video quality in case you do not need the highest quality (e.g. in case you want to reduce the disk space and bandwidth requirements), and you might have a better UI (and otherwise use your own implementation of various software).

About subtitles, something else I sometimes want to fix is adding an outline to the text and adding a translucent background (many use a opaque background (making it hard to see the picture) or a transparent background (making it hard to see the text)).