A swamp cooler is designed for less humid conditions that is why. Think Arizona, New Mexico area.
A minisplit has an evaporator on the inside that has a fan that sucks room air in through a coil that conditions it and spits it back out, a condensate pump and line to move the water. The evap. is connected to a condenser placed outside with refrigerant lines connecting them. The condenser converts the refrigerant basically making it cold again, this conversion puts off a lot of heat and noise.