If I remember correctly zprezto started as a huge pull request to oh-my-zsh that the author rejected. You can probably find it in the closed issues of oh-my-zsh.
TL;DR: Robby Russell wanted out-of-the-box functionality for newbies, and auto-updated turned on. Sorin Ionescu wanted better tailoring for experts and didn't want the auto-update which he saw as annoying.