I don't really have a good answer for this because I think about it in different ways. To me, The Gift was a much more powerful finale, a better finale and probably would of been a better series finale. However, I do love the happy ending and the hope that was seen in Chosen so I am glad the series ended with that one. I always wanted Buffy to be able to be free and happy, that's what she always wanted. On how the finale's affected me though, I cried during the Gift and it was very emotionally powerful to me. I didn't shed one tear during Chosen and thought it was so-so. The scene with the scoobies in the hall of the school seemed awkward and forced, and none of it affected me much (and this from a person that was Buffy obsessed since the movie in 92). I really never got attached to any of the potential slayers and didn't care much what happened to them, or if any of them lived or died. I cared about what happened to the core group, and to Faith, and I'm probably one of the few that kind of liked Kennedy (she was no more annoying than anyone in s7).
The first 5 seasons I feel were the very best, especially seasons 2, 3 and 5. I'm very happy the show went on though because I enjoyed season 6, especially Bargaining, Afterlife, OMWF, Tabula Rasa, Wrecked, & Seeing Red through Grave. I thought having Willow go dark was a great idea and the 4 part finale (I always considered it a 4 parter since each epi started right where the last left off and I think it happened over the course of 2 days) was excellent. In fact if the show had to end early, Grave would of been a good finale. Except then we would be left with the Spike cliffhanger. Season 7 is probably my least fave season. Reasons: the annoying potentials I couldn't seem to care about, not many episodes just focusing on the scoobies, too much First stuff and too early, constant Buffy speeches, plotholes, the setting seeming to constantly be inside the Summers house, specifically the living room, and just lackluster episodes. The Wood subplot was never exciting to me. It had some good episodes though and ended nicely.