but if you play slowly you don't net 5 of 10, you net 3,5 of 10 .
Don't think so. If you play slower you'll have less runs and so will your oponent, because he's able to make a run every time you end one. Same for you.
More probably, since you're waiting for a better chance to take shot due to lower pace, your overall shoting quality will be increased making, let's say, a 6 of 10 nets.