Its not really a matter of 1 being better than the other. Most amplifiers will produce more power with a lower impeadance load. In other words if an amp produces 150 watts into 4 ohms, it will likely produce twice that into 2 ohms. 2 ohms is half the impeadance of 4ohms, providing less resistance for current to flow thru. That assumes though that the amp has enough nuts in the power supply to provide the extra current. What the different voice coil impeadance's are for is to allow flexibility in wiring your speakers and amp. The higher impeadance loads are generally a little easier on the amps. However you dont get the full power the amp is capable of producing unless u drop the load down. On some amps that can be as litle as .5 ohms which for all purpose is just about a dead short..