Marquis only played 6 minutes of SF in the first game, and 10 minutes at SF in the second game.
For whatever it's worth, I had Marquis at about 8 non-Pierce minutes in Game 1, and 13.5 minutes with Paul out of the game in Game 2.
If that's accurate, that means Marquis gave up 17 points to Lebron in 21.5 minutes (although, again, some of these points were off turnovers and techs). Without Marquis at SF, Lebron scored 49 points in 65.5 minutes.
Lebron vs. Marquis: .79 points per minute, 44% shooting
Lebron vs. everyone else: .75 points per minute, 45% shooting
Whatever the difference is there, it's pretty negligible, especially when you take into account that Marquis played many of those minutes beside Nate, Semih, and BBD, while Pierce got more time with the starters.