The weather will be better in Israel than in Boston -- either in late March OR in late October.
As I noted before, look at the calendar for the Jewish holidays: Israel gets a LOT cheaper to visit after the fall holidays are over (which won't happen until the last week of October in 2016), but you probably don't want to be paying the premium to be there as a casual tourist over Passover (again, not an issue for March 2017).