whats the difference between these two

SPK04 - 4 Ohm Extension Speaker Box
4 Ohm Extension Speaker Box with Lead and Plug
Features
High performance elliptical 4 Ohm nominal 3 Watts maximum 5 Watts

SPK07-Dust/Water Resistant Extension Speaker
Dust/Water Resistant Extension Speaker with Lead and Plug.
Features
8 Ohms Nominal 2 Watts maximum 3 Watts dust/water resistant speaker
i know the more watts the louder it is depending on amplifier etc but Ohms???
What's your thoughts on the better speaker
Jase