This months issue of Rapid Magazine has a write up on both these boats, and they are great reviews! The mamba and diesel have very different characters. I would encourage you to pick up the mag.They say the Mamba is intermediate to advance boater running bigger water and creeks.
They say the Diesel is fast and punches holes easily, along with the fact it has harsher chines so play boaters feel more at home in this boat because of the similarity of playboat edges.
I've got the newest Diesel 70, and all I know is that it's easy to roll, very quick, a sports car in the curves and very stable on edge.