A separate issue about relative value of StackOverflow vs. ServerFault: How quickly does the underlying technology mutate, such that yesterday's correct, best-in-class answer is no longer a correct answer at all? I'd argue that programming probably has a longer 'tail': languages are by design backwards compatible: yesterdays answer will still work, even if it's not the best.

Admin solutions tend to age more quickly: once a particular class of hardware is end-of-lifed, or software has had a major rev., how to deal with its quirks of configuration is of little or no help to the next generation. And the admin interfaces to software tend to be the least designed, most user-unfriendly part of the system.