"ac•cu•rate" 1. In exact conformity to fact: errorless.
Yes, GPS is more accurate than levels. The reason for that is because the accuracy criterion for First-Order Geodetic Leveling is an error of closure of (±3mm/km). To achieve accurate leveling results in the State of Louisiana better than the capability of GPS, it would therefore be necessary to start at an accurate benchmark within 28 miles of the eastern border of Louisiana.
However, research has proven that the closest accurate (reliable) benchmark to Louisiana is east of Mobile Bay, Alabama!
Therefore, GPS is more accurate than levels in Louisiana, because of subsidence. However, there are no accurate benchmarks close enough to Louisiana to allow leveling results equal to or better than what is possible on a day-to-day basis with dual-frequency GPS receivers.