Revolution has a more refined and tweaked battle system, 4 player tournament matches, ultimate jutsu combinations, more characters to fit in with where the Japanese Anime is currently at as well being the last Storm game. It also features additional backstories that have to do with Shisui and Itachi, Akatsuki's formation, Kushina and Team Minato. I don't know if the Main Story Arc and Mecha Naruto/Tournament thing is one Story blended together or a separate thing as you might have seen. Also, these games do tend to leave out a lot of details and circumstances from the anime and manga.
As for content and playability, well it depends on how much you like fighting people online or whether you are more of a single player kind of person. I've done a little number of Multiplayer matches online in Full Burst. But there was enough to do in the Open World of Storm 3 and I'd fight the CPU alot. So you have to take that into account. Overall I would say don't try to branch off and get into something you are not really a fan of by buying a game or movie. Because I would recommend Revolution only to the biggest and most die hard Naruto fans since it is really a Spin Off from the main story mode experience.
