I think Kris is probably a better all-around musician than Adam, but Adam is more the showman. Kris can sing, play at least two instruments well, arrange songs and maybe write songs (I'm not sure about that). Plus, he has a very "radio friendly" voice and style.
Adam's style is especially suited for live concert, the stage, etc., and I think he can also write songs. But both guys are easy on the eyes, and Kris, supposedly, has the AI folks backing him (maybe in addition to Adam?).
I'm feeling a bit of deja vu -- it's 2003 and AI2 all over again?
Of course, the rules have changed since then. The AI people are way into supporting the also-rans, since about Season 5 (when Taylor foiled Simon's plans and won). And all the top 10 get to release full-length studio recordings of songs for purchase on iTunes and to radio. That changes the name of the game (and I hear Kris has actually beaten Adam sometimes in that area). This should be interesting.