If you want "safe" the pick is easily Burleson. he has a nice, soft match-up with Detroit, and he has a stable QB throwing him the ball, and he's also put up solid numbers for most of the year.
Crabtree, however, offers vast potential. He has 50+ and 80+ yards in his two starts, and is making his home debut (like you said), and it's against a Tennessee defense that is one of the weaker secondaries in the league.
Crabtree is my vote, simply because he's getting better, and he'll get looks. Besides, the 49es will struggle at running the ball against the Titans solid run d.