Rivnuts from Homestead, PA on 12/2/2019 5:33:05 PM:
That depends on your priorities including travel logistics, physical conditions, preferred accommodations, etc. The biggest difference that most riders cite is the topography. From DC to Washington makes the 23-mile section from the Eastern Continental Divide to Cumberland a downhill ride whereas in the other direction it is an uphill ride. It doable either way depending on your preference.
Travel logistics to/from Pittsburgh and Washington, DC are the other most common factors in choosing which way to ride this trail.