To the basic gist of the thread - AL baseball has been better than NL baseball for quite some time. It's almost certainly the DH, which allows managers to rest regulars on occasion and it forces AL pitchers to face longer, harder line ups where their NL counterparts can walk #8 to get a nearly automatic out. Rob Neyer wrote about this some time ago during the PED era. He noted that 1) suspected PED use was more common in AL teams 2) he suggested that the many pitcher friendly parks in the NL protected pitchers so they threw the more traditional fastball, change, curve whereas smaller AL parks + DH made pitchers adapt so you saw more types of pitches in the AL. Lastly for a long time the top payroll teams resided in the AL so they can buy out the talent. We'll see Bryce Harper in the AL pretty soon and it's unlikely that a guy like Machado is going to leave the AL when he hits FA. Because the DH helps protect the longterm deals, it's easier for AL teams to give a guy like Harper all the money.