I guess I can't speak for everything but most plastic hides are solid plastic and most plastics made for the purpose of holding liquids are not porous at all. Soda bottles that lose carbonation aren't seeping carbonation through the sides of the bottle- they are losing it as the seal of the cap deteriorates.
In any event, its pretty established that wood is going to harbor much more bacteria and mold than plastic ever would. And all things being equal, just giving you the benefit of the doubt, its even more established that plastic is many many more times easier to clean and disinfect than wood.