Is it better to use nizoral twice a week or shampoo daily?

Hi, I have MPB (NW2.5 or so) and am on propecia. I wanted to ask about Nizoral and Head and Shoulders. I've been told that pyrthione zinc 1% in H&S may help with MPB. I use it daily. Lately, I've heard that Nizoral is more effective but it is too harsh to use regularly. I was wondering: Is it better to use nizoral say 2x per week or H&S daily (or some combination thereof)? What evidence do we have on the effectiveness of these shampoos? I'm looking for the best regimen possible. Thanks.