Okay, I'll throw in here, but a little late:
We drive from NC to Mass. (outside SW Boston) twice a year, and have basically went both routes (95 vs. 81/77). goofyforwdw is correct, the diff. in miles is around 50 (Checking our notes, the trip from mid NC to Mass is 40 miles longer by going inland, and the other trip leg from here to WDW are almost equal, 40 to 95 vs. 77/26/95). Our driving time is faster inland, by avoiding the major 95 cities.
The only major snag we have hit going inland was the dreaded GW Bridge (as we cut across PA south of 84), which we have sworn off now. We now take the Tappanzee, and drop back down to 95 in CT.
The inland route, the possible snags are Roanoke, VA in afternoon rush (small poss.), and Charlotte, NC either a.m. or p.m. rush (big delays poss). Both of these added together pale in comparison to any of the major I-95 problem areas.
Speed limits are similar between routes, except you will have more VA miles, where there was no 70 mph (only 65) speed limit, and radar detectors are illegal.
Inland tends to have more commercial traffic (i.e. big trucks), but overall is not nearly as crowded. Much more laid back than when we have taken the 95 route.
Hope that helps. If you have questions, feel free to send them.
Robert P