Revolutionary War hero Patrick Henry was a pretty dramatic dude, best known for his famous either-or statement, "Give me liberty, or give me death." This is an example of what is known as a false dilemma; it's "false" because our pal Patrick could have chosen a third option, like jail. Boiling down a dilemma to two extreme choices creates a dramatic effect.
It's no mistake that Patrick Henry makes a lot of appearances in Atlas Shrugged. Many of our main characters either taught at or attended Patrick Henry University. The novel seems to really embrace the either-or choice, too: reality is what it is, you're either for us or against us. In terms of philosophy, this book leaves very little wiggle room.
But philosophy isn't always easy to act on in the real world, and choices are rarely clear-cut or simple. Atlas Shrugged frequently complicates its own love of either-or options with characters like Cherryl, who is really lacking in choices, the confused Eddie, the frightened James, and the impotent "looters." Even the strikers and our heroes are unable to always deal in absolutes and black-and-white options. Dagny especially frequently wades through murky options and makes choices that defy the "either-or" of the strikers and the looters, going for a third option instead.
Choices are perhaps more plural than Galt's philosophy suggests. It's possible that Galt and his strikers, much like Patrick Henry, are seeking to create the absolutes and the either-or choices they want to see in the world.
Dagny is the unintentional epitome, or fulfillment, of Galt's values. By frequently going against both the strikers and the looters, she is a true individual who makes choices for herself alone.
Though Galt expresses his values in terms of either-or choices, the book as a whole demonstrates that either-or options are often more of an ideal than a reality.