Bigger is better. Bigger magnet, bigger voice coil, better faster response. Bigger cone, more bass. Bigger box, well you get the idea bigger is better.
That said, impedance and efficiency are important. Especially if you will be driving all 4 off the one amp, then you want to be sure it will be able to drive them all at once. With mine, thanks to having two amps I was able to compare them wired for 4, 8 and 16 ohms. While they deliver more power into 4 the bass was much better by far at 16. According to Duke none of his customers who have compared have preferred 4 ohm. Something to keep in mind when comparing speakers.
That said, impedance and efficiency are important. Especially if you will be driving all 4 off the one amp, then you want to be sure it will be able to drive them all at once. With mine, thanks to having two amps I was able to compare them wired for 4, 8 and 16 ohms. While they deliver more power into 4 the bass was much better by far at 16. According to Duke none of his customers who have compared have preferred 4 ohm. Something to keep in mind when comparing speakers.