Scott Simkus has posted some fascinating data from his vast collection of box scores for exhibition games pitting Negro Leaguers and major leaguers against semipro teams.  Definitely check out all three posts, as well as the comments.

UPDATE 12:50 p.m.  Scott has added a post on the records of different semipro teams vs. major league and Negro League teams.  The Brooklyn Bushwicks come out on top, at 58-60.  The 1921 Tesreau Bears, who were 21-15 against Negro League teams, were probably somewhere close to that level.  And the Long Branch Cubans, who played both Negro Leaguers and major leaguers extensively, would be interesting to throw into the mix.