Empire side - Brunwulf Free-Winter. Balgruff's the only second runner... yet he's someone who talks tough, but is ultimately spineless. He accepted the Dominion's demands not once but twice. He could have sided with a free Skyrim under Ulfric,
Stormcloak Side - Ulfric Stormcloak. He's the one who saw the problem, identified it, and took action to rectify it. He's the one who actually put the effort and risk into organizing, building, and maintaining a successful rebellion that can stand against the Empire. If the High Throne is a responsibility, he has proven himself capable of handling it. If the high throne is a reward, he is the one who has put in the effort and labor to earn it.
Of course, both options are inferior to Nazeem. It will take years, but he'll earn his way to the top. He'll be in charge of Skyrim, a very successful province, obviously. Do you go to High Hrothgar very often? Oh, what am I saying, of course you don't.
He advises all of the Jarls of Skyrim, and his input is very invaluable.
Of course, as HIgh King, it's all probably a bit over your head. If you were getting Nords from his province, they'd be twice as strong.