Gotcha and understand.
Note however, that CV stage will be longer with higher current so a portion of the minutes saved during CC stage will then be lost during CV stage. Other variables obviously come into play as well (charge lead length and gauge, battery internal resistance, etc.) that could further reduce the differences. I do completely agree that the PL6 will offer greater power and lower charge times off 24 volts than the 306B. A 15% reduction would be a reasonable expectation, in my estimation.
Have not followed the PL6 thread for a bit but wondering if Tim and company are pondering a firmware update that will raise the input current limit to, say 50A, in similar fashion when the PL8 power was increased via firmware update. I'm sure this would make a lot of folks happy...