sort of....when a motor turns and its movement is coverted by gears then you open up some options if you alter the gearing ratios.
A "high torque" setup will result in the sector gear spinning "slower" but with more torque/power. That's good and sometimes necessary for high powered springs. Your motor will (or at least should) operate more within its ideal operating parameters and your battery should last longer (vs. a setup that's not geared appropriately to pull a stiff spring).
A high speed setup is (largely) the opposite. The sector gear spins faster but with less torque. Good for lightly powered guns when you want a high/large RPM.
Reliability only slightly factors into it. Most of the reliability will come from setting the mechbox up right (shimming, etc...).
Airsoftmechanics.com has some great write ups on gear ratios. Lots of reading there.