The problem with Henderson is that for a guy who's background is primarily in martial arts, he has done a poor job closing the deal with a knockout. As a matter of fact, only two of his career wins have come via the knockout.
That is a rather poor record when someone is used to delivering high impact shots. His eight career submissions look good, but Edgar is not going to get caught in that. Henderson will have to knock the Light Heavyweight champion out, and that's simply not going to happen.
Edgar has only one career loss, and he eventually avenged that with a knockout. Traditional logic is that you need to beat the champion with a knockout or make him submit to get the title. If that can't happen, the decision has to be obvious.
There is nothing in Edgar's career to suggest that he will lose that way. We're talking about a guy that hasn't lost anything in nearly four full years. This is a fighter still in the prime of his career, with the championship, and in a strong matchup.
Ultimately, the matchup is what this really comes down to. More than who the better technical fighter is, how the two match up to each other will decide the fight.
Edgar has played strong defense throughout his career, losing only one fight (which came via decision). His knockout career is no more prolific than Henderson's, but it doesn't need to be.
The only thing Edgar will need to do is play defense, pick his spots, and capitalize on mistakes. Anyone who doubts that he can do that needs to remember that this is the champion who has defended his title three times.
After tonight's bout, it will be four times.
Prediction: Edgar by unanimous decision