I prefer the later seasons. There is a bit of a nostalgia factor for season 1-3, but I find Buffy and the scoobies far more relateable in the later seasons. Buffy is my favourite character and in the early seasons she often seemed so whiny, wanting a normal life, hating being the Slayer and not being able to combine the two satisfactorily. I much prefer and adult Buffy, Family-centric in S5, dealing-with-the-dark S6 Buffy, and even The General Buffy of S7 - those versions of Buffy are much more appealing to me then teen-girl Buffy, and become even more so the older I get.