Originally Posted by Padfoot Patronus
First, this is not active vs. passive voice. Both of your examples use the active voice. Passive voice would be: "His head was rested on the table."
As for which is better: as others have noted, it depends on what you want to emphasize. If your character is describing the scene, then the first one is more of an observation of what s/he sees. If your character is describing what the other person is doing (if, in fact, that other character is the current topic of the paragraph), then the second example makes the character more of an active participant in the scene, as opposed to something the narrator is observing and remarking upon.
I think what follows the semi-colon makes a difference. I would recommend, for example:
"His head is resting on the table; the room is dark and quiet."
"He is resting his head on the table; he's obviously been up all night."
However, this is very much up to your personal preference, since in any of the above examples, you could switch phrases without it sounding wrong.