I love Vernon Davis. The cat can flat out play when he's healthy. Just don't confuse his play for consistent. He certainly provides you with the most reward should he continue to improve.
That said, I still say you go with Olsen against Detroit. Remember, San Fran is a run first team...and no team with Cutler is a run-first team. Olsen is consistent, and IMO, the #1 target in Chicago.
Go Olsen...although you likely won't go wrong with either.
"All my friends now...they look up to me...the wish they could be...a lot more like me..." DLR