Here is a link for the entire 2007 season... Splits
2007 SplitsUsing those stats, I actually did some cyphering on my own. I know, that's dangerous!
Here are some things I found interesting...
LHH vs RHP hit .15 points higher than RHH vs RHPs.
LHH vs RHP also walked nearly 4 more times out of 100 ABs. RHH struck out one more time out of each 100 ABs.
Much bigger discrepancies showed up with LHPs.
RHH vs LHPs hit .20 points higher than LHH vs LHPs.
RHH hit a HR against LHPs one in every 31 Abs, while LHH vs LHPs hit a homerun once in every 40 ABs. LHPs also walked RHHs at a higher percentage and struckout LHHs at a higher percentage.
Probably the most telling stat is the Batting Averages
RHP vs RHH .262
RHP vs LHH .277
LHP vs LHH .261
LHP vs RHH .281
This is using the stats for the entire 2007 MLB season.
Note, There are many RHPs and LHPs who absolutely dominate the same side hitters. The left hand specialists are on most teams. These guys are most often lower arm angle guys with exceptional breaking balls and or sinkers.
This is also true for some starters, ie Randy Johnson in his career has given up 369 HRs. 345 of them were to RHHs. RHHs hit only .221 against him, but LHHs hit a much worse .195 with an unbelievably low .286 slugging %.