Peter Island is more expensive and has fewer mooring options. It is not that protected a harbor from swell and the snorkeling is no where near as good.
I am not suggesting either clockwise or counter clockwise. The sailing distances from Norman to anywhere you want to go are very easy. We left Port Purcell on our last charter and made it all the way to the North Sound at Leverick 1/2 motor (no wind in beginning)...1/2 sail in just under 5 hours (or five caribs)... So, add 30 min to that form Norman. Not appreciably different when on Island time.
Anyway, you really cant go wrong. It is only a difficult decision because every option is awesome!
Keith