I'd say Gohan wins with mid-diff as long as Cell doesn't get a chance to fight tactically by using combinations of Taiyoken, Death Saucer and possibly Life Drain if he can still use it, or use his regeneration tactically to win via war of attrition.
Grade 2 boost is insignificant by the time one has mastered SSJ IMO. If, for the sake of the thread, you want him to get the same boost as Vegeta (post 1st ROSAT), he stomps.