The problem with larger woofers is that they are slower than smaller ones.
I am not sure where this concept started but there are many who share this view.
IMHO, the single biggest factor in fast or slow designs is the speaker Q or resonance. Overdamped (Q of about 0.5) sound fastest whilst critically damped speakers (0.7) sound moderately fast and underdamped designs (Q of 1.1 and higher) tend to sound slow and often boomy. Unfortunately, the lowest Q designs are the least efficient and therefore they are hard to find. REL appears to be a low Q design (it has low group delay) and this, IMHO, probably has more to do with why they sound more musical than other subs (not woofer size).