I just got 2 subs to compare the difference. AR PR1212 and the Paradigm PW-2200. Both are 250W RMS but the Acoustic Research sub has more sound and has way more SLP than the pw-2200 at the same cut off and gain level. Both 12" but the Paradigm cost 3 time more than the AR sub. I hear great things about the Paradigm but did I get a lemon?
Placement can make a HUGE difference. So if you're listenting to the subs side-by-side, make sure you use identical positions for the subs as well as your listening position. If the AR is situated in a corner and the Pardigm isn't, that could explain some of the difference.
Otherwise, go with what sounds good to YOU. I think too many people buy based solely on specs, which as I'm sure you know, are questionable in almost any case, even from very reputable manufacturers. Why? Because environments vary. Because testing procedures vary. Because test equipment varies. Because tolerance levels vary. It's absolutely true that you generally get what you pay for, but if the AR sounds better than the Paradigm for one-third of the price, well, I guess the Canadians have a little work to do.