player wise, MJD > B.Marshall, but if you look at score, B.Marshall average 3.3pts more than MJD, and that's in .5 PPR league, probably close to 5pts in PPR league.
assuming you are starting 2 RB, 2WR 1 RB/WR
if you take MJD, BJGE will be your flex
if you keep B.Marshall, B.Lloyd will be your flex
and i definitely prefer B.Lloyd > BJGE
afterall, it'll depends on how many RB and WR you start in your league, but trade value itself is pretty even