yes maneto is the main factor.. If he will join the fight then xmen will win easyly.. Otherwise maybe difficult for xmen to win this fight..
I'm also not convinced that Dr. X going inside the Hulks mind would be the same as going inside other peoples mind. He might have more control because the Hulk isn't too smart or he might not have much access in there because there are 2 minds in there. Has the Hulk ever had a Psychic hero get into his brain?