The only difference is what amplifiers can and cannot power it. For example, you should be able to power a 3 ohm subwoofer with a 4 ohm stable amplifier. Whereas you'll probably need a 1 ohm stable amplifier to power a 1.5 ohm driver.
However, if you're talking W7s, which I think you are, then it's not going to make much of a difference as the 10W7 and 12W7 are 3 ohm drivers and the 13W7 is a dual 1.5 ohm driver (can be wired to either 0.75 ohms or 3 ohms). If you get into 2 of them, then it makes a difference ...
Voice coil configuration makes little difference when it comes to SQ and SPL ...