New characters, new developments, etc.
I really don't have time to watch it, and I'm confused by some stuff in Gaiden (like the onion head Uchiha).
Basically: Naruto is really popular in the village, a lot of girls want him to be their boyfriend, Sakura tells Naruto why he never really loved her, Naruto spends half the film being all awkward around Hinata, we get a bunch of touchy feely moments that should have been in the manga to justify NaruHina, Toneri is a major bad ass who kidnaps Hinata's sister, they go on a rescue for her, Hinata allows herself to be kidnapped to save Naruto, the ninja villages get together to blow up the moon using a weapon the Raikage created, Sasuke pops in to destroy a meteor, Sasuke goes off to destroy meteors to protect the village, Naruto fights Toeneri, Hinata helps him defeat him, and then Naruto has children.