In the last two weeks my wife and rented both the movies Juno and Bella, you can find reviews of both by clicking on the title. While both movies have a similar plot line, I would describe them as polar opposite movies.
Juno is described in the review I linked as a movie that does give a glimpse into teenage culture. You see into the world of sex, language, family dynamics, and many other things. For this reason I would say that it is a good movie. As I sat and watched, about half way through I remember looking at my wife and saying, it is nice to see the future adoptive father, be portrayed in a somewhat quality way. Well I had spoke to soon, because by the end of the movie the guy has turned into a guy and father that we see portrayed in tv and movies to often. He shucks all responsibility to live his life.
Bella takes all the good elements of Juno and keeps them, but removes all the bad and exchanges it with good. In Bella we see friends looking out for each other, we see a quality family dynamic that is in no way perfect, but very loving. We see responsibility taken for decisions made.
The problem is that Juno will probably be watched by twice as many people as Bella. And Juno will be the one labeled as more culturally accurate than Bella. My encouragement is if you are going to watch Juno you need to watch Bella. And if you have teenagers that are going to watch Juno, please talk to them about it and then watch Bella with them. Bella will not appeal to teenagers as much as Juno will, but it is worth the watch.