if we’re talking about which holds in moisture the best, aluminum foil is better because it is less permeable. Permeability means the ability of a substance (liquid or gas) to pass through it. For example, if you poured water through a pasta strainer, it would fall right through because of all the holes. But if you pour water into a solid bowl, none of it will go through because the bowl is less permeable. The plastic wrap may look solid, but if you zoom in really closely you would see tiny little holes that the water can escape through over time. The foil also has holes, but they are way smaller than plastic wraps. That’s why water evaporates through the plastic more easily.

Here's a science fair project, comparing evaporating with different kinds of plastic wrap:
science project

My sheets of foil from Costco have tiny holes in them [I don't know why]. I could compare evaporation, using Costco foil sheets, with evaporation using foil from a roll of foil without holes.