Vets sell science diet because they make money. Every vet I've talked to "swears by" the food they sell in their offices since they make money off of it from the producers. Stick with a holistic brand that ALWAYS puts meat as the first ingredient. Holistic is better than most other foods and is usually cheaper. Hill's makes Science Diet and the prescription diet stuff. It's all crap.
I swear by raw food and I've never been happier with the results. If you don't want raw, stick with holistic like Solid Gold, Innova, or Royal Canin. I've never heard of natural choice so I can't give much input on it. Hope that helps!