On the other hand, since it only cost you $5, you can easily spend a bit on basic aluminum-rimmed wheels with all the money you saved.

The new pads you got have helped, yes, but aluminum rims really will help more.

Also, keep in mind that the other end of the braking system -- the tires -- affects performance as well. Fatter tires with more rubber on the pavement will stop quicker. Even between tires of the same size, older tires or new tires with hard compounds won't brake as hard as grippier tires.

The practical, real-world difference between V-brakes and calipers really comes down to tire clearance, not braking power. That's why you won't see narrow calipers on hybrids and mountain bikes.