I don't see why PEDs would effect the performances of two completely different types of athletes in ways that perfectly balance out. In fact, I'd be shocked if they did. I doubt it's a perfect balance, but pitchers would seem to benefit greatly from the use of steroids, considering how useful steroids are when it comes to muscle recovery. A relief pitcher on steroids throwing on three consecutive nights is probably going to suffer less of a drop-off in his stuff on that third night as opposed to a "clean" relief pitcher. A starting pitcher on steroids coming off a 120-pitch effort in his last outing might come back stronger in his next couple starts than he would if he wasn't on something. Pitchers are more likely to benefit from the ability to bounce back, recover from injury or avoid injury. They aren't that likely to be that much better of a pitcher. Steroids won't help get movement on a fastball or break on a slider. They might help throw harder, but the ability to throw hard isn't necessarily a strength thing. Hitters definitely benefit from swinging harder. So steroids might prevent teams from having to use their weaker replacement arms as often, but expansion played a part in negating that benefit.