What's the difference between a lever-style manual pump and a silicone (Haakaa-style) pump?

A lever pump like the Medela Harmony or Lansinoh uses an active hand-squeezed piston to create rhythmic suction, so you control pace and pressure and can fully express a breast. A silicone pump uses passive suction, you squeeze, attach it, and let natural let-down flow in. Reviewers across r/breastfeeding consistently note silicone pumps are not true replacements for expressing on both sides, they're best for catching let-down or relieving engorgement.