I downloaded navfree. As the name implies, the app is free, allthough, the download size is really big. And you have to download different apps for different countries. But it's free and works. I don't have a comparison though, because I never searched for an alternate solution.
I use AT&T nav when im riding shotgun with friends works perfect, only thing is i pay $10 a month. When im in my car i use motionx because its compatible with my radio and is visible on the radios wide screen and only cost $2 if im not mistaking. But only a one time charge.
I've been using waze. It's great and it's community it's awesome too. Your able to post things for others to see on their maps. Like construction police etc. and your able to see what others have posted as well