Vernon Davis in a heart beat, The guy is an unusual monster of nature with his speed andability for his build and size.
Davis will be the goto check down guy for alex Smith, who has Antonio Bryant to throw to and most likely he will be rushed and have to throw down to his speedy and tall check down TE Davis.
There really is no one to steal catches in SF, i would want Davis as my backup any day of the week, he can burn safeties deep easily.
KWII on the other hand is coming back from injury and is playing with the same type of QB who isnt the best, but has Jurevicious, Edwards and Northcutt to steal passes from him, but i did hear they will be splitting him out at WR some, but i dont like the chances of him of a guy like Vernon Davis.
I hope this helps