Jon Bois of SB Nation wrote this interesting piece about how professional football teams would have performed if they played all of their games. Not too much to gloss into--99% of all the teams tend to play better at home (save the Miami Dolphins, who should probably be excised from the league based on these numbers).
When you look at the Bay Area teams, you'll find some of the typical results--the Golden State Warriors, Sacramento Kings, San Jose Sharks, Oakland Athletics, and San Franciscowould have performed modestly better if they played all their games at home, which seems like a total duh if you think about it twice. Familiarity with the arena/ballpark/ice rink tends to breed better results.
However, what's most interesting is the results for the NFL.
If the San Francisco 49ers had played all their games at Candlestick Park, they probably would have won the NFC West the past three years and Mike Singletary wouldn't be out of a job. The Niners performed nearly 20% better at home than they did on the road, and Alex Smith might be considered a semi-competent quarterback rather than one that needs to be tarred and feathered on Market Street.
Interestingly, for all the mystique of the Black Hole in Alameda Coliseum, the Oakland Raiders offer the worst home field advantage. Play all their games at home, and the Raiders are projected to finish with the same record. Al Davis would probably be outraged by this if he wasn't a skeleton.