Just to pick a nit, there are more outs "per capita" from flyballs than from ground balls, at least at the mlb level. The big question is who is giving up more line drives? If a pitcher can give up mostly fly balls and/or ground balls they will do fine more often than not. More hits come on ground balls but far fewer extra base hits so they tend to have similar results overall. Every pitcher is different and should play to their own strengths. For some that is being a fly ball pitcher and for some that is being a ground ball pitcher. It is the line drive pitchers who are in big trouble as going from a faulty memory it seems that about 20 or 25% of fly balls result in hits, 33% of ground balls result in hits and 70% of line drives result in hits. Of course 0% of strikeouts result in hits. In other words, try to avoid solid contact in whatever way works best for you.