Jim Halpert is manlier due to his ability to embrace his feelings for Pam, and do what he has to in order to overcome her engagement to Roy. He progresses up the chain of command in Dunder Mifflin faster than Dwight, probably makes more money, and also supports his family better. Not only this, but Jim also proves time and time again that he is capable of getting into Dwight's head, which is on the forefront of important abilities when it comes to head to head battling.
I'm pretty certain that Jim's marriage to Pam only shows that he is too weak to take on the world alone. Furthermore, Jim only rose up to higher positions through kiss-assery, something only a wussy-man would do. Dwight proves time and time again that he is capable surviving as a lone wolf. Did you ever think that Dwight chose not to rise up the chain of command so that he could further enhance his farming abilities? Some of the most manly attributes a person can have is the capability to plant, grow, and harvest a crop, especially beets! And so, Dwight is the better man.