>>2912710>>2912695STM technically has the best optics of the three. Aberrations and flaring is controlled more (due to a new coating) but it's essentially the same Gaussian optical design. But it does have more and rounded aperture blades so Bokeh is much more smooth and creamy overall.
AF though, while accurate and the quietest of the three by huge margin, is still not technically silent (you can hear in on-board audio in movies) and is actually the slowest of three.
I still wouldn't hesitate the recommending the STM over the older nifty-fifties, unless you want the mechanical manual focus and distance focusing scale (get the MK I). There's literally no reason the get the MK II, unless you're next-level poor.
