Which episode is sadder?

I would say, "The Body", in part because of how effective it conveyed death and grief. But part of my reasoning is, in a sense, not quite a fair assessment in that, though Buffy's death in "The Gift" was poignant and tragic, when it occurred in the series broadcast not only was her death at the end of the season completely spoiled in the press, but it was a foregone conclusion that by some means she would be back since the death occurred at the end of the run of the series on Fox and everyone knew that the show was coming back on UPN. So unless it was going to become "Faith, the Vampire Slayer" or something like that, there was no doubt that her death was not final. While such outside knowledge shouldn't take away from the drama within the story, in the end it does (and even for those who did not see the series during the original broadcast, the impact of her death is mitigated somewhat by the knowledge that there are two more seasons to go).