the bevel-pinion method results in full engagement of the motor pinion. way quieter, way more efficient, less wear all around. you really need to try it and see the results.
The only times they sound whiny is when people are using flat gears
believe me man, in the 3 or 4 years I've been working on my gearbox(es), I've taken it apart and reshimmed it so many times, trying to get it right. a bevel shimmed gun (preferably with a mosfet) is something special to behold.