Of course, my vote went for Simba.
To me, Simba's a much more interesting character. I relate to Simba a lot more than I do to Kovu. Each of them have their own unique qualities as an individual. Kovu just wanted to live a better life and be with Kiara. He didn't want anything to do with Scar and couldn't even relate to his enstranged guider because Scar wasn't his father and died before he was born. He had to escape that perdicament of following Zira's plans to kill her archenemy and rule the Pridelands. On the other hand, Simba dealt with a real loss of his wonderful father after his own uncle killed him. He had to deal with isolation from his homeland after being exiled over the years and had to figure out his place in life. Simba finally figured out who he was, took responsibility as the incoming king and faced Scar for good. He had to fight off a real murderer for whom he thought that Scar was his "friend" as a cub. A real hero takes as much action as possible, no matter how much it hurts and restore reality back, and that's exactly what Simba did.