Taperlock is by far the most common out of those two, however they're normally only available in steel, which if you want to accelerate/decelerate things fast, can add a noticeable bit of weight and affect performance. They are however common place across lots of industrial applications, meaning they're readily available.
Alloy pulleys, properly keyed on is a far lighter option, and much better where you need to change speeds quickly. I wouldn't rely soley on a radial grubscrew to transmit drive, and would look at some form of proper lock. Be that a key, drive pin, taper pin, bolt/nut, or grubscrew/bolt axially between the pulley/shaft.