Um...depends. Madara said a person with one sharingan can never achieve the true potential of a person with two sharingans. Plus, in a sense, Kakashi and Obito represent one entity because of their shared eyes. Kakashi is the good side and Obito is the bad side of that body, both sides are different yet equal. Symbolically, they are the opposite ideals in one person that eventually clash with each other in order to see which is right. Though both have equal strength, the person/belief that holds the most conviction will prevail. So, long story short, Kakashi can defeat Obito, it all depends on who's beliefs are stronger.
