I am not sure if Oakley apply a film or laminate the polarising layer inside the lens. The latter is better quality.
If you imagine throwing a handful of light into your eye, some will hit it direct but a ton of it will enter the eye at funny angles. This creates glare, a bit like a blur of light. If you can only allow the light in that hits your eye centrally then you reduce all the other crap and just get the direct light. No glare, crisper image. This of it as reducing TV static, but from your eyes.
I think sunglass lenses reduce horizontal light, only allowing in vertical light. This drastically reduces glare (especially from lakes, windows, mirrors and shiny surfaces, which in turn makes the image you see appear sharper. Also, the brighter the light is the more glare you get, by cutting that out you will effectively be able to see more of the non glaring stuff.
Given a choice, based on a reasonable cost difference, I would run polarized.