Depends if you are adding teeth to the front sprocket or the rear. Think of the sprockets on a 10-speed or mountain bike, same principals apply. The more teeth up front, the more speed you have, but you give up torque. More teeth in the rear any you have greater torque at the expense of speed.
Something to think about, if you go with too few teeth up front, the chain has to bend around a tighter circle. This can prematurely wear your chain out.