It all depends on the weather. You cannot say for definite what will be better. The vis could be buggered next week or so going on the recent activity from Ex Hurricane Bertha still having adverse affects. It's not too much of a drive between Osmington & Portland at all, just take it as it comes. If you are in Portland then it's either the east or west side depending on the wind, tide, swell, but be careful of the currents as they do flow quick. I am no expert on Portland by the way so I'm surf others may post what will be better.