Why the choice matters more than it looks
Every delivery decision is made by pattern-matching against people who already triggered your optimization event. Choose a frequent event and the algorithm accumulates real examples quickly. Choose the rarest event in your funnel and it is guessing, because it has barely seen anyone do the thing you asked for.
Frequent, but still meaningful
The trap on the other side is picking something so shallow that anyone triggers it. Optimizing toward a page view teaches the system to find browsers. Pick the shallowest event that still indicates genuine intent, then move deeper as volume allows. On Meta this interacts directly with learning limited; on Google, the equivalent question is whether your bid strategy is pointed at the conversion goal at all. We work through the Meta case in don't optimize a new Meta campaign for purchases.