On Gehringer v Robinson:
Gehringer played longer, has more hits, Hrs, extra base hits, everything really. Has a slightly better OPS, slightly worse OPS+ but Gehringer was awful his last 500 ABs at age 38 and 39 (Robinson retired at 37). They both had 4 great seasons but Gehringer had 7 seasons of OPS+ higher than 135 to Robinson's 5. Gehringer had a slightly better fielding percentage and a slightly better range factor although Robinson had the bigger gap from range factor to league average RF for his time. Gehringer had better post season results both in hitting and in team success. Robinson finished 1st in power/speed ration but Gehringer not known for his speed, also did it twice. Gehringer was top ten in runs 12 times, Robinson 7 times.
IMO Robinson is overrated which isn't taking anything away from his contributio to the game. If we had to consider that he'd probably be a top five player ever but we are talking straight skill and career accomplishments here and Gehringer's numbers are just better. Had Robinson played 5 more years he would have probably passed the guys I have listed in front of him. Both were great, Gehringer was just consistently great over a longer period of time.
Actually looked up the numbers on these guys. A few comments:1. You say that Gehringer had 7 seasons of OPS+ higher than 135, which means you are counting a season in which he played 5 games and had 13 plate appearances. Misleading IMO.
2. Two of Gehringer's OPS+ seasons higher than 135 occurred before age 28, and 5 after age 28. Robinson wasn't allowed into the majors until age 28, so they both had 5 such seasons in that comparable age span. Meanwhile, Robinson had 3 seasons of 150 or higher, compared to zero for Gehringer.
3. Robinson has a higher career OPS+. You attempt to explain this away by saying that Gehringer played poorly in his last two seasons at ages 38-39, while Robinson retired at 37... but you apparently make no allowance for Robinson missing very productive years before age 28 due to discrimination. That seems unfair IMO.
4. You mention power/speed ratio, but not the more general topic of baserunning. Robinson was an outstanding baserunner and I assume better than Gehringer.
5. You say Gehringer had a better fielding percentage, but actually Robinson had a better fielding percentage and a better differential compared to the league average. Was that a typo on your part or did I miss something?
All in all, while admitting that I don't know much about Gehringer, Robinson looks like the better player to me... better hitter, better fielder, and better baserunner. The only reason to credit Gehringer is that he played longer and played a lot more games at 2B. But to credit him for that means not crediting Robinson in any way for the years he was forced to miss, which doesn't seem right.