Jafar is the best choice here. Commander Rourke would act friendly and then stab you in the back, and Percival McLeach is just an unhinged lunatic. Prior to becoming Sultan and transforming into a genie, Jafar was just a cunning sorcerer looking for power, and you could probably actually work with him. And unlike Shan Yu, Jafar actually does seem to be friends with Iago at least in the first movie, with him complimenting Iago's "evil mind" at one point, so yeah he's your best chance of not being murdered.