AOE actually can correlate to power. We have no other measure to go by when it comes to how strong Aokiji's attacks are.
Jozu[
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Doffy[
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Despite being directly applied in Jozu's case, there isn't any difference on the ice covering their bodies. The ice affecting a greater area indicates more power in the one used on Doffy, as it is the same ability in both cases. At the very least, the attacks were even, and that still plays in Doffy's favor. Either Doffy broke out of an attack that is equal to the one that defeated Jozu, or he broke out of the one that is stronger. Either way, Doffy is portrayed as above Jozu.