That's a really good point about the different run-scoring environments between the AL and NL in that time-period. I guess we'd need a contextualized RS+ / RBI+

That's a really good point about the different run-scoring environments between the AL and NL in that time-period. I guess we'd need a contextualized RS+ / RBI+ statistic that I'm not smart enough to generate, but maybe someone on Baseball Prospectus already has. Biggio was my favorite of the "Killer B's", and he'd have found a place in any lineup in any era. The power-hitting leadoff guy is a recent (analytics-driven) trend, so it's probably the correct approach - I just wonder if Ricky wasn't such an outlier (and it's not even like he didn't have some pop, too!) that I wonder if he doesn't confound the model. I'd be equally as interested in the converse to the (very good) added question you propose: which of them leads in first-inning RS rate?