When I go to either of these locations it is with the purpose of covering the basics or getting preliminary information. Maybe to get a history on a particular area, discover what sources they have for transcriptions of marriage documents, wills, or land records. I have found some very random collections at each repository. The library has quite a few books on Pennsylvania, the county archives has a nice collection on Virginia and North Carolina. Not exactly what you would expect of local holdings is it?
Once I've exhausted the local repositories for information, I can make better use of my time at the Tennessee State Library and Archives (TSLA), which is at least a 25-30 minute drive. Once at the state archives I can focus on more detailed work like the manuscript collection, surname vertical files, books that aren't available at the local archives and newspapers. Even better, since I found a transcription in a book at the local archives, I now know what microfilm to focus on when I get to TSLA.
Basically it all comes down to making better use of my time and the resources offered at the state level. So the moral of the post is; state archives are wonderfully vast in their holdings, but don't ignore or discount the holdings of your local repositories. You just might be pleasantly surprised.