Sheldon Brown was right about most things, and he was right about gear ratio and crank length, however poorly he explained it. Crank length is a personal preference, and even riders with identical body dimensions may want different cranks, dependong on the strength or flexiblity or training. But really, cyclists obsess over the difference between 170 and 172.5. The difference between 165 and 180 is only 9%, or less than one gear change.
Get over it.
em