Most Helpful Girl
If he is doesn't have a defined jawline in the first place (for example: the guy in Arwen's fire's pic), then stubble would make him look unkempt.
But if he has a manly, defined jawline, stubble would make him look better.
But stubble always make you look older/more mature, so if that's the look you're going for, then go for it! =) Clean shaven makes a guy look younger.