By the way, I did some research recently.
Rank when it comes to Jutsu isn't a measure of power. It's a measure of power, utility, and how difficult it is for the average person to learn.
All other things equal, the stronger jutsu with be a higher rank... But we actually have a canon example: Raikiri/Lightning Blade is an S-Rank technique, but Kakazu's Lightning Release False Darkness technique, which is roughly equal in terms of raw power to the Raikiri, is only a B-Rank.