First off, I'm going with Dallas. Here's why:
People are saying that Kyrie Irving's defense is bad. Last time I checked, Jrue Holiday wasn't an offensive juggernaut. Plus, another year of experience on offense for Irving makes playing him on D that much more difficult for Holiday.
Chris Bosh is soft. He's an Allstar, a solid offensive rebounder, very good midrange jump shooter, but he's soft. He doesn't like to bang, and I can tell you right now Brand and Varejao like to bang(let's be mature here, everyone; no giggling, OK?).
To me, Thaddeus Young is not a PF. Sure you can play him there, but I don't think he'll fare well against a guy like Jeff Green who has a polished post game.
Wade's on the decline, and Thabo Sefolosha is smacking his chops. Imagine, just for a second, if Wade wasn't the athletic freak that he is. With that athleticism draining more quickly, I can see Sefolosha stopping Wade or Pierce.
Finally, LeBron James. There's a reason he was the first pick in the 2012 CB Draft. There's a reason he's the best player on the planet right now. Don't be surprised if he averages a triple-double in this Finals series.
Done with matchups. On to team play:
I think we can all agree Dallas has the better defensive team. Chicago has absolutely no post presence, and Dallas is incredibly athletic on the perimeter. If Chicago tries winning this series on jumpers... Well, good luck with that.
Dallas has a much more versatile offensive lineup than Chicago. They can post with Green, LeBron, and Brand, or take it outside with Irving and Gordon.
Chicago's got Dwyane "I like to gyrate in the air when going for a layup just to get a foul call" Wade, Chris "jump shooting big man" Bosh, and Paul Pierce as their options on offense, against an elite defensive team.
Overall, when you've got the best player in the world and an up-and-coming star guard, you will probably beat two stars on the decline and a soft Allstar.
Dallas in 6.