What is the difference between Quiet regulars and the win-back ladder?

Timing and who they are for. The win-back ladder on Marketing → Loyalty & stamps chases anybody whose last order is a set number of days ago, in up to three stages. Quiet regulars, its own card under Marketing, watches each regular's own rhythm and nudges them when they are well past their usual gap, before the ladder would reach them. It never fires for anybody with fewer than four orders, never within five days of an order, and never on the same day as a win-back message. One is a calendar, the other is a habit. The Loyalty & rewards tab in the docs explains both.