Tough to compare since their forehands are so different, and are built around their respective games. That said
Margin for error: Djokovic
Running forehand: Sampras
Rally ball: Djokovic
Sampras' forehand was a big shot, but it wasn't very versatile. If his forehands were not coming off, it's not like he could play it safe and hit penetrating rally balls. Technically he could but that wasn't going to win him a lot of points against the likes of the best baseliners.
I don't think he was particularly good at handling high balls either with his eastern grip, which is probably why he struggled on clay.
But it was such a huge shot that opponents were not comfortable hitting to it - observe how selectively Agassi would hit to that wing, especially on fast courts.
Djokovic's on the other hand is not as forceful as Sampras's was, or for that matter, Federer's. But then he doesn't need to go for as much, because he has such a great backhand, plus superb defense.
He can pretty much do anything with it when it's on, but he doesn't have Pete's sheer explosiveness. And Sampras' running forehand is legendary for a reason. There's no comparison there.
I wish there were more men like Atticus Finch around.