I would say that it's probably best if you go with a High Torque gears, and an M110. Reason being is that it slows down ROF so that you don't really "spray" as much or at leas shouldn't rely on it as much (that's just a personal thought, not like it's based on anything as well because it slows your ROF, if you're in a "spraying" situation it will empty the mag slightly slower so that might be better).
As for thinking about them.... Think about the difference between bike gears (not really the best comparison but it should do). In a "low gear", you pedal fast and it's east to pedal but you don't get that much "power" and might then up going at 5 km/h, whereas in a "high gear" you pedal slower and it's harder to pedal but you get a lot more "power" and thus might be able to get lets say 30 km/h pedalling at the same RPM as when you were in a lower gear.
Also, helical gears when shimmed right and with the right motor height will be quieter than "standard" gears not shimmed right and with the motor height slightly off. It will still make noise but not as much.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE