From the standpoint of Boston winning, I'd much rather have Love play.
Love's average game is going to be better than Nance or Green. *But* Love's ceiling six games into this series is pretty well established. He's a problem for them on defense. Al gets off great shots against him in the post (what is he shooting, something like 75% at the rim against Love?), and he's not an active help defender. He also makes it easier for us to keep Baynes in the game. Baynes has been a plus team defender and capable switched onto LeBron. His rebounding has been good for a few easy putbacks a game, which can really help with momentum. Basically, when we play against Cleveland's bigs, I think we have it figured out how to beat them.
Nance or Green make the outcome much harder to predict. They *might* take a dump on the garden floor and gift us the game. But they might also bring a lot more energy to the Cavs' defense and rebounding, and on a good night Green will get you as many points as Love.