I have to say for me it was Chosen. Angel lost my love in season 4 (not their fault, just bad timing from Charisma Carpenter's pregnancy meant their story arc was all mushed and kinda creepy with whole Connor thing). But Chosen did pull back some of what made Buffy great in the first place. Female power, strong team work, great acting and good comedy moments. It was more rounded than some of the other episodes in that season.

That said, NFA provided one of my favourite scenes in the Buffy/Angel sphere. Spike getting drunk, getting on stage, doing his best known poems (the one he wrote and performed on the day he was sired) and getting a huge applause from an audience of tough biker type dudes. Brilliant.