Chosing a Voice

I am working on a novel and I've finally fleshed out enough of the plot to start actually writing the scenes. The book has 3 important characters. Lets call them 'Good #1', 'Very Bad', and 'Good #2'. Good #1 is who the readers should identify with, at least at first. 'Very Bad' is still very important though, and part 2 is to belong to the this person. Part 3 is where 'Good #2' shines and sets up the future. 'Good #2' will become 'Good #1' for any future endeavors. Can you tell I'm an optimist? All three of these characters are important throughout the book but the focus changes for each part.

My original intention has been to write a 3 part book using first person voice and actually changing who the 'I' character is for each part. However, now that I sit down to write it I lapse immediately into third person view. So I have a dilemma: should I keep third person and just run with it or do I write however I can fill the pages then go back and rework it into a different voice? (Check out this great article for explanations and examples of the different voices.)

I wanted first person for the depth it could bring. Nothing pulls you into a character more than reading it like it's a character's own personal journal. And I believe that it's important in this book to pull everyone heavily into all 3 of the characters. But can I have the same effect if I use third person, possibly third person objective? Will the difference between "I have to do this" and "She knew she had to do it" be that great?

I really don't know. So for now I'll write however I can. I'll tell the story and manage the details when I must.