I wouldn't rule out martinez at a comfortable weight but in all honesty oscar was just a different class of fighter.
Oscar wins it. What has Martinez done to be considered such a great fighter? He's not fought anyone near the calibre of Oscar. Martinez is a very good fighter with a couple of good wins and a thin resume. Oscar was a very good fighter with an absolutely solid resume despite losing some fights. Oscar wins, by knockout.
I respect the idea of Oscar beating Martinez, but no way does he knock him out. Martinez would be giving him angles and would not just stay there going toe to toe. Martinez is a smart fighter and remember he's more comfortable at 154 and Oscar never was.