So...did we get any spoilers?!! I was busy writing big essay on why I like Nami but Fu*k!!! Never analyze a main character, never.
Main characters do not grow substantially and on top of that you gotta go through 1000 chapters for analysis and it is a head-cracking task.
Always choose a character who has had less exposure in terms of panel time, but at the same, when he/she did get panel time, it provided a window into their character e.g. Sabo.