I posted the same poll in another forum, so I'm gonna give my same thoughts here.
Personally, I like them all for opposing reasons:
'Prophecy Girl' ends in, more or less, full resolution. We have few questions when the credits begin to roll.
'Becoming Pts 1 & 2', however, leave us with many musings: How will Buffy return to Sunnydale after all she has is gone?
'Graduation Day Pts 1 & 2' bring us Angel's departure and a prophetic riddle from Faith that forecasts Buffy's death in the years to come.
'Restless', like Faith's riddle, also offers foreshadowing of events to come, as we have seen develop during the sixth season.
'The Gift' gives us empty promises of happiness (i.e. Xander's marriage proposal, the reinstatement of Tara's mind, Buffy's remarks to Spike) before we watch Buffy descend to her death.
'Grave' has little resolution: How will Willow deal? How will Spike return? Will Dawn gain a sense of independence? How will Buffy respond to all these issues?
I think 'Grave' might actually be my favorite simply because it does end rather ambiguously. I like that things will have both form and chaos when the new season begins.
I must add, however, that 'Becoming Pts 1 & 2' are absolutely excellent.
