I realize the OP is probably past it all by now but thought I'd add a little bit, hopefully it adds some value.
1. I-95 between the Susquehanna River and Richmond VA is almost completely done being widened, repaved, rebuilt and or repaired. Between Baltimore and DC there are 8 or so lanes in both directions, so barring a major traffic mishap or bad weather, you should be able to slide right down with no problems, especially at non-peak times. Between 10pm and 4am you'll feel like you're 60 miles west of Amarillo. South of DC, there are EZ-Pass lanes and plenty of room pretty much all the way to Richmond.
2. Between Wilmington and Annapolis on US-301/50, there are about three traffic lights (around Middletown) and then half a dozen or so in Queenstown. The only really busy stretch of the road is south of Bowie, as mentioned, after it splits from US-50. Waldorf, La Plata, Bel Alton can be stop-and-go on US 301. Once over the Potomac and headed towards Bowling Green and then Richmond, it's not bad at all.
So the bottom line is, all other things being equal, 301 is good for a change of scenery, and for my money is still more "relaxing" from Wilmington to Richmond, but is probably not any quicker or easier, now that I-95 has improved, and US 301 has gotten more built up.