Just what are the benefits of PED use for baseball players?

Yesterday, major league baseball announced that San Francisco Giants outfielder Melky Cabrera tested positive for excessive testosterone, earning him a 50 game suspension.  Now, the debate has begun again, just like it does anytime an athlete tests positive for PED use, as to just how much of an advantage he or she gained by taking the banned substance.  The problem is, there is no clear answer to this question.

The reason this question cannot be definitively answered is that there is no way to isolate the effects of certain PEDs in a controlled laboratory setting (also, it would be nearly impossible to receive approval to conduct a study where these types of drugs were given to human participants).  There are numerous factors that effect the performance of a baseball player, including, but not limited to, hand-eye coordination, amount of practice/experience, motivation to perform, psychological status, muscular strength, muscular flexibility, etc.  While it is true that Cabrera's batting average has increased 91 points in two years, the effect that the excessive testosterone had on this increase cannot be determined.  Every other factor that could cause improvement in batting average cannot be controlled in order to isolate the effects of the testosterone. 

Now, I am not advocating the use of performance enhancing drugs.  They definitely can help cause increase in muscular strength, and they definitely have some very bad side effects, and they should not be allowed in athletics, as using them is a form of cheating.  However, scientists and researchers cannot quantify specifically how much of an advantage these drugs give an athlete.  Also, the punishment for a first time offense in both MLB and the NFL is not severe enough to discourage athletes from experimenting with PEDs.