Good topic. It’s nice to "get the low down" on subwoofers from guys with a lot of experience with the subject.
Adding to the small vs large conversation:
Its been stated that speaker distortion is directly proportional to the movement (excursion) of the cone. Double the excursion, double the distortion. Cut it in half ... half the distortion. Taking the popular 10" and 15" driver sizes as an example, the 15" has to move less than half as much as the 10 to produce the same volume of air. Assuming that things are somewhat linear here (the "motor" in the 15" has sufficient power to do what it does well), the 15" will be cleaner at a given frequency and sound level. So, what about the added "mass" of the 15? We have to keep in mind that some of the "added mass" is the weight of the air itself. At the same frequency and same volume level, the "weight" of the air being displaced will be exactly the same. The differences will be the moving mass of the additional cone material, larger voice coil, etc. on the 15" which will be minimized by the cone moving less than half as much as the 10". Cone breakup is another form of distortion on larger cones that may also be offset by less cone travel being introduced. The quality of the execution by the manufacturer will be a key element here, but it is entirely possible that larger woofers will, in fact, have less overall distortion and produce "tighter" base than a smaller woofer.
We ordered in a 31" raw woofer many years ago because we were "hot rodders" who liked to mess with outrageous stuff. A 31" woofer has more cone area than 6 12" woofers, as a reference. I recalled mounting this thing in a 6 cubic foot sealed enclosure and running some test tones thru it. The rafters were, literally, shaking all over the building. A walk back to inspect the woofer revealed that the cone was moving about 1/4".
There’s no substitute for cubic inches.