When talking SPL score, large cone area does not always equate to a higher SPL.
Many factors come into play, like.
enclosure airspace,
Cabin airspace,
cone weight,
cone strength,
power compression,
impedance rise.
Am I forgetting anything?
Case in Point, I am friends with team BK who competes in dB Drags SS-NW.
Last year they had an Astro running 2) 18" DD 99Zs. They topped out at 161.6 dB and after that they were shredding cones.
Early this year they tried 15" 99Zs and score went up to over 162 and subs were not blowing at all.