Answer: Iorek
One thing to note - this is more of a subjective answer than an objective answer, so I do not think there is a "right" answer. Here is what I think:
I believe Iorek would make a better king than Lofur. While Lofur is cunning and able to maintain power, he does so through deceit and betrayal. Iorek, on the other hand, is an honorable and just leader who values the well-being of his people. He is willing to fight for what is right and is intelligent enough to come up with creative solutions to problems.