I think McAvoy put an entirely different spin on Charles' personality with this reboot. Don't get me wrong, I adore Sir Patrick Stewart's portrayal of Xavier in the first X-men movies, but that Xavier is a much more benign, almost saint rather than the creature we get in First Class.

McAvoy's Xavier is much more approachable for the viewer. He's down at the pub, he's hitting (and failing) on girls, he has terrible pick up lines - this is not the calm saint who barely bats an eye at anything. McAvoy's Xavier is closer to the Xavier we, the viewer, can relate to; he's got failings, he's not the untouchable saint on a pedestal. He's got no problems using his powers to manipulate the FBI/CIA, he does put his fellow mutants first over humans and is very protective of them. I view this as far different from the peace pushing, everybody love each other Xavier from the first few movies.

Now I get to the part of First Class that bothered me, in regards to both nu!Xavier and nu!Erik's characters: the beach scene, before the missiles. Erik comes out of that sub with a massive personality change. We don't really get a heads up to the grandiose speech that falls out of his mouth at that point. During the whole movie, Erik is a Nazi hunter (GO MAN KILL 'EM ALL), a terrible motivator, dead sexy in a turtleneck, and Protective!Erik when Charles is about to get squished on the Blackbird - but then, he does a one eighty and goes all megalomaniac and preachy. There is something in that scene that just does not jive for me. I would have bought it - right up to the point where Charles reaches out with his mind to confirm the missile strike. Charles, up to this point, has agreed with Erik about his protective stance towards mutants. So why the ever loving FUCK does Charles make a plea for Erik to save the humans when he knows that the military will just fire again?

And, for that matter, why didn't they fire again? Didn't think about that before, but the captains should have said, fuck it, let's try again, because there's a threat to be eliminated on the beach. So, unless something happens that the viewer doesn't get to see, it makes no sense that Charles and company were just left on that beach, free and clear.

Sorry, left field. Where was I? So. The rift at the end of First Class doesn't make a lot of sense to me. During the entire movie (and even after the damn beach scene) we see a Charles that's dead set on protecting his mutants from harm, up to even wiping a human's memory clean - so why the fuck does he disagree with Erik on the beach? Yeah, I get that Charles would be all about not killing people - BUT. I think his character should have known Erik's personality enough that Charles would have argued against killing the humans so that they, the mutants, could mitigate the horror that's about to come down on them if Erik did go about with the return missile strike and not tried to argue that the men on those boats were just following orders.

As for the comic-canon Xavier - I remember a Xavier that sat in the gray areas a lot more than the noble shining saint of the first few films. There was a particular issue - god I can't remember which, but it was the one where Magic died from the Legacy virus and the Professor, for reasons I don't remember at the moment, can walk for the day, and Jubilee takes him roller blading. The First Class Charles reminds me of that guy and not Stewart's portrayal of the man.

I guess one other problem I have with Charles being set up as a saint is that he's a telepath. He's probably seen the darkest part of every person's soul. He should at least be a little more pragmatic than Stewart's version - and McAvoy brings a little of that to the stage with his version of Charles. So I guess that's why the ending of First Class drives me a little crazy with the need to fix the fucking thing.

tl;dr - Stewart played Xavier as a saint on a pedestal. McAvoy gave Charles feet of clay. We dig the feet of clay, man. He's much more fuckable.