I would go for Wonson first keep that, then go for Pusan and burn that. I would burn it as I think the site 1SE is better as it would get the gold resource in the BFC. There is one city Ulsan which we have not yet found, I think this is south of Wonsan, this would be in Tundra so more than likely a poor city. If he will vassal once he is down to Ulsan, Cheju and Nampo then I would take that, if not then burn as many of them as it takes.