Sakura is incredibly useful until Sasuke gets involved, and then she becomes a drooling fan girl. Her healing skills, strength, and intelligence are all very high. It has been a long time since I saw The Last Airbender, but I don't remember Katara having as much character development or extraordinary skills. All of her skills were similar to Sakura, but on a smaller level. Of course, now that Naruto is more on par with DBZ, most anime is on a smaller level when compared. Final summary:
Old Naruto Sakura < Katara
Post-DBZ-Naruto Sakura > Katara