Congrats. Both are top-tier champs, so I think it comes down to personal preference and your roster. I voted for Kitty Pryde because of her utility. Overall, I think she's more sustainable. Her phase mechanic in particular comes in handy in many tough fights. Although her damage when fully ramped up is more than respectable, I'd suggest her if you're more interested in utility.On the other hand, if you're mostly looking for a damage-dealer and you're comfortable with Professor X's mechanics for gaining and maintaining prowesses, he's probably the better call. With enough prowesses, his damage is second to none. Also, he has his share of utility (counters evade, has falter, power control, etc). Plus, he boosts the special attack damage of mutants.