With respect to the issue of speed, I think it should be pointed out that most everybody gives Mays, and to a lesser extent DiMaggio and Mantle, credit for defensive excellence. That’s in part due to their speed. Speed is a major factor in an outfielder’s defense, less so at other positions.
None of the other candidates for Best Player of All Time were as good a defensive player as Willie Mays, but there does seem to be a big range of speed value:
Willie Mays - Very fast
Honus Wagner - Very fast
Mickey Mantle - Very fast for some of his career, average for the rest
Ty Cobb - Very fast
Barry Bonds - Fast
Joe DiMaggio - Above average, although in his day you didn’t try to steal bases
Hank Aaron - Average, but a smart baserunner
Babe Ruth- Average, reckless baserunner
Ted Williams - Slow
The question is what difference it makes. Speed on defense is already being considered; nobody compares Mays to Ruth and Williams without acknowledging the monster difference in fielding value. But how much does baserunning speed matter?
I would guess about 10 runs a year, max. The best basestealer in the lot is probably Barry Bonds; Cobb stole more, but Cobb also got thrown out probably 350 times or more (they didn’t count CS for a lot of his career.) Bonds has stolen 506 bases and been thrown out 141 times, a very good ratio. Going by Pete Palmer’s method - which isn’t great but for this purpose it works okay - that’s worth about 75 runs. Or, over the course of Bonds’s career, like 4 runs a season more than someone like Williams who pretty much didn’t run at all.
Now, Bonds’s speed helps in other ways. For instance, Bonds has grounded into only 141 double plays. Williams grounded in 197, in fewer games than Bonds. That’s worth 20-30 runs. But we’re only up to 5 a season. Even adding on a few more runs for extra bases on hits, 10 is the most you’re gonna get.
Over the course of a career 10 runs a season adds up, but that’s the difference between the BEST basestealer here, Bonds (I imagine Cobb, Wagner and Mays would have similar advantages) and the very slowest, Williams. The difference between those men and an average baserunner like Hank Aaron is more like 4 or 5 runs.