I am gradually coming to the conclusion that SLG is the most important batting stat in all of baseball.
I think I could sum up my hypotheses at this point as:
1) OBP was an independent force only for a select 2-3 players a year only around the 19th and early 20th century (those 23 of the 46 with .400 plus OBP and SLG under .400 and batting averages below .300).
2) OBP has never been and is not now the most important offensive factor or stat.
3) OPS has two problems as the stat to focus on: 1) it already includes OBP, which since SLG looks at total bases, assumes and incorporate OBP into itself as a stat, and then it compounds this problem by doubling the OBP presence within OPS - the bases achieved inherent in SLG plus the OBP measure; and 2) it confuses the actual relationship of cause and effect between the two (this is ALWAYS a problem with empiricism - so Mr. AJ Ayers and Mr. Karl Popper please sit down - you too Francis Bacon ! - and Mrs. Imre Lakatos and Mr. Theodor Adorno please take bows for having pointed out that this would be a limit of empiricism, thank you).
OBP is clearly largely caused by SLG - by home runs and other slugging. It has been since the rise of home runs in the 1920s, and before that was only somewhat independent of SLG and AVG anyway, an independence that, despite the massive marketing campaign about OBP and OPS, has basically not shown up since 1961 as we saw above.
4) A walk is NOT as good as a hit. First, because as we are finding, the best way to get a walk is to be a dangerous hitter, high SLG gets you on base. Second because a hit usually can move runners up two bases or even three, not just one, and the point of baseball, and the cause of run production, is not primarily getting on base - since we saw when we looked at WHIPs under 1.00 (see the other thread in this forum) that except against the very best pitchers every season, until the recent era's use of relievers, it was normal to get at least one person one base each inning on average. Further, a walk can only drive in a run if the bases are loaded, so that OBP is even dependent on itself in a weird snake-eating-its tail way - unless three other teammates have gotten on base, you can't produce a run with a walk, but SLG can clear the bases with the push of a button.
5) Therefore OPS masks the reality that only one of its constituent components - SLG - is really the cause and the other - OPS is an effect and of less importance.
However - I could be wrong - these are hypotheses, derived from the data (since as Lakatos taught, the purpose of all research, including empirical research, is to produce theory, that is to learn something new), but we still have a lot of data to look at. We need to take the study of OBP over .400 and SLG over .500 to the present day and then also look at the examples that could derail my theory - cases of players with high SLG but low OBP. Such cases might show that SLG is a necessary but not sufficient condition for high OBP, for example. So, let's move ahead.