Well, from what I recall, the akiko is supposed to be able to do 8-bit c2p conversion about as fast as a 68040.
Therefore, I assume on sub 68040 systems it speeds up c2p conversion a lot compared to software only c2p. By the time you get to 68040, most routines run at copy speed so actually writing to the chip ram takes longer than the conversion and akiko begins to make less and less difference.