Aha, but consider this:
-A single can move a baserunner with speed two bases a significant % of the time.
-A walk will sometimes not move a baserunner at all.
Runners at second and third:
-A single can result in 2 runs.
-A walk results in 0 runs.
Just messin' with you UN, because I realize you already know those things quite well.
A little statistical analysis on the relative value of a single vs. a walk would be interesting.