Sealed subs will generate more harmonic distortion but less phase distortion. Harmonic distortion is generally a lot more audible than phase distortion. Group delay is a type of phase distortion. But this all depends on how either the phase distortion or harmonic distortion is manifesting. Lots of group delay at higher frequencies would be pretty audible, and if the harmonic distortion is comprised of higher-order components, that is also very audible.
Also, no modern loudspeakers or especially subs are made in accordance with acoustic suspension principles that were advanced by Edgar Vilchur in the 1950s. Back then, the magnets weren't as powerful, so they didn't act as well as the restoring force of the moving assembly. These days the magnets are so much more powerful, especially in subwoofers. The motor is overwhelmingly the restoring force unless the moving assembly moves so far out that the suspension tension is what restrains its motion.