Usually it's a function what temperature you want to get down to. The suction pressure of your lowest stage is typically kept slightly about atmospheric to avoid leaking air into the process through flanges. The air would accumulate which in a HC system would not be good from a safety point of view. Given you are constrained to atmospheric pressure, propane gives you about a -40F temperature at sea level. Butane would give you just above the freezing point of water.
Ethylene plants can have an ethylene refrigeration loop similar to a propane one because ethylene will give you an even lower temperature.