I think people are getting the wrong picture here,Simba is not my favorite character,Mufasa is. But yes,Simba is on second place and he's definitely someone I would defend as I find him being a great example. Many people like Kovu,actually most people do,as I do. Don't think that someone doesn't like him just because they like someone better, Simba for instance.
I say that Simba's past can compare. But it's all up to you,I can't dissuade you into believing what I do,as you have your point of view on Kovu and I have mine. Your vision of Kovu's past is obviously much darker than mine is.
Simba has been through his life thinking one thing all the time 'I killed my father.' ,which is,from my point of view,a MUCH harder burden to bear than being trained to kill someone. You might want to tell me that he spent his life in the 'Hakuna Matata' fashion. Yes he has,but do you know why? I know why,it's all just a defensive mechanism of Simba's personality. He couldn't live his life mourning for his father loss,his personality then so to say blocked out that fact and made him live his life he did. It was too much for him to handle and that's how he dealt with it eventually. That's how most people deal with things like that,the mourn in the beginning and then they ''move on''. However,one can never get past something like that,which Simba didn't,he proved it at the end.
Kovu didn't kill Simba because Kiara came in the way. If it weren't for her,who knows how it would have went. I would say Simba would beat Kovu,but you'll probably tell it the other way,which is perfectly fine,it's up to you what to think about it.