Well I'll just call a spade a spade. IMO Emin is better, pure and simple. Obasi doesn't have a chance with Emin. Emin is shutting him down before it ever begins. You don't see the other two doing that.
I think you're comparing apples and oranges.
In the first video, they're not competing. Obasi isn't trying to "fight" Emin, and he isn't trying to win; he's just letting Emin demonstrate on him and teach.
In the Randy Williams video, he's just trying to over power Williams.
Honestly though, I think you should be clear about your intentions. If you want to learn, go ahead and do Chisau. But if you just want to fight, just fight. Don't confuse one for the other.
Edit: I just noticed there were 5 more pages of posts that I didn't read...