well, it's like "full-size blazer vs. 22" rims. which is better?" dual 3 is the impedance configuration, and 3, sounds like 3" diameter. i think what you were directed to look at was the impedance configuration, and power level, to match your amp. i'm taking it you are comparing a jl w6/7 to something else? not many d3 subs out there. if you have a 1.5ohm stable jl amp, then it would kind of match. however, some amps, you loose a little rms at 1.5, and some you don't. what is the configuration of the aluminum coil? what sub is it?