changing sprockets will change things around a little bit, its all about mechanical advantage.
the smaller the front/larger the rear=more low end but less top end
larger the front/smaller the rear=less low end but more top end
this can be simply calculated by dividing amount of teeth on the rear sprocket by the amount of teeth on the front.
going 1 tooth one way or the other is like going a 3 teeth in the opposite direction on the rear, therefore larger changes should be made with the front, and the rear used to fine tune