This comparison is intrinsic to the premise of my work. First, there is no way to perform a comprehensive comparative analysis of all great players regardless of era without attempting to neutralize the time period. Sure you can compare Mattingly to Hernandez, their deviations from their league mean, do the same for Greenberg and Klein and then rank them. But that gross negligence overlooks the many ways the game has changed, or allegedly changed: the rules, philosophy, strategy, free agency, stadiums, road conditions, bullpens, night games, discrimination, technology, expansion, farm system optimization, official suppliers (Spalding/Rawlings), manufactured materials (For one, I certainly believe the league experimented with the ingredients in the centers of the baseballs esp. btw 1920 - 1934.), culture of performance-enhancers, and on and on and on... Now I can't possibly account for all these variables, but what I can do is acknowledge that there's a difference between 1924 and 1954, 1937 and 1977, 1974 and 1994, then and now. My plan is simply to try an neutralize the time periods, by placing adjusting all players stats to current levels (2010-14). Two reasons I prefer the current time period, the perceived balance, relevancy/marketability (I'll likely publish my full results).
Anyway, the comparison btw Speaker and Cobb is interesting because they played in the same time period, where Cobb clearly outplayed him. The purist would order me to stop there, but to maintain consistency, they are both translated into the current period. And their performances are reversed, Speaker emerges as the better, most complete player. I did a full analysis on my excel file, but I just wanted to share an excerpt in a comparative analysis of what I estimate to be their best individual seasons. Obviously, both of these single seasons have been adjusted to 2010-2014 levels.