The reason the atypicals are so frequently used is because of the side effect issue, but the typicals have been proven to be as or more effective, so picking the one with the least side effects is what you and your doctor need to do, but often it is a matter of trial and error. I don't think you can make the generalization about positive symptoms without considering each medication separately.
You can try clozapine. it's atypical and mostyl peopl find it the best one, and btter than the typicals. It helps many people who didn't get better with other antipsychotics.Good luck.