Many manufacturers wildly inflate their HP numbers -- OS being particulary guilty.

The 70 4-S will be close to the 46 AX 2-S, but maybe a bit weaker. A 91 4-s is certainly going to outperform a 46 2-S, but at a penalty in bulk & probably weight. An 80-size 4-S is probably a more sensible choice for a 4-S.


However, this simplification ignores the power delivery characteristics of the 2 types. You have to decide for yourself what you want from the model.

A hot 46 2-S will rip around very nicely, but with the associated wail from it's high-rpm operation. An 80-size 4-S will also blast around, but with the typical put-put sound of a single cyl 4-S -- your choice.