When a sub reproduces a 40hz note (for example), that means it is cycling 40 times per second. If another sub reproduced that 40hz note 'slower' or 'faster' that would mean its no longer cycling 40 times per second, and would be playing a completely different frequency, which is obviously not the case. Point being, calling subs faster or slower is indeed a poor description of the differences in group delay between setups.
What a few people here have said is 100% correct, the enclosure design (alignment mostly) is key to getting your system to track well with the transient nature of the material being reproduced. Im not a Kicker fan much these days, and agree their designs tend to revolve around output more than SQ, but even an L7 can be made to sound decent in the right box. Problem with the square cones is (or, one of their problems), they require a larger enclosure than a comparable round sub. Kicker neglects to mention this when suggesting their square coned subs have more cone area than their round counterparts. They want us to believe you get that added cone area with no downside, which is simply untrue.