Can you (or anyone) explain where the power density improvement comes from with axial flux? When I work through the first-order math it seems like it should com

Can you (or anyone) explain where the power density improvement comes from with axial flux? When I work through the first-order math it seems like it should come out the same as radial flux. Is it just that the geometry allows better cooling from the coils? Or the use of grain oriented steel?