Quoted from Zdoor:As a current Xmen and Avengers owner, I like Avengers better. I like my Wolverine and have it dialed in and pimped out nicely. But, Avengers is a better game as they sit right now. It is a great machine with really good sound effects and music. The voices are fine to me. They're not perfect but they are not bad and the script is pretty good.
I'm in the same boat and agree 100%. I'm really enjoying Avengers, much more than X-Men at first. X-Men has been growing on me as of late, but Avengers clicked with me right away.