Statistically there is not that much difference between them, Messi is better with the ball than Ronaldo, and has that extra magic. But i will say this though, Ronaldo is in no way a bad player with the ball, i think he is a top player with the ball. Not that magic of Zidane, Ronaldinho, Messi etc. But he contributes very well when he gets involved. Sometimes i wish he got himself more involved, he obviously has the ability to create danger.
However, i dont think the difference is very big between them, and in my opinion Ronaldo has had a better season.