I didn't focus on that but anecdotally I find that consistently oversleeping (over 9 hours) would leave me groggy and generally reduced performance (at least temporarily in the morning) but not as bad as sleep deprivation. Whereas getting one or two nights of mild oversleeping after being sleep deprived for several days does seem to speed up the recovery time.

Of course there were many other variables like exercise, diet, health, and mood, where each seems to have some minor effect on my sleep requirements one way or the other. The Sudoku benchmarking was performed on more or less "idling" lifestyle (no unusual healthy or unhealthy activities, and I wasn't consuming alcohol/caffeine or smoking).