At the end: story telling and plot >>> powerlevels. As long as Oda wants them to be equal, he'll make them equal.
I’m pretty sure that Oda’s thought process was “Roger and WB are equals, so I guess it would make sense for their crews to be equal too,” not even considering that fact that MJV are still only teens, the WBP aren’t even as big as they were in MF, and Prime Ray was portrayed as at least Admiral level in his clash with Kizaru, in which Kizaru himself said that he would need help if he was gonna try to capture Old Ray.
In this very same chapter, Roger and WB did 0 damage to the island they were fighting on for 3 days, and to make matters worse, their crews were fighting too. Ace vs BB caused more collateral damage. Birdcage even caused more collateral damage. This chapter just shows us that you shouldn’t take power scaling too seriously