Lily or Willow?
Considering by the end of HIMYM end she would have been Lily LONGER than she was Willow (a good run for any near 40 year old actress IMO)... who do people see her now... Lily or Willow?
shareMostly Willow.
BtVS is a much, much, much greater thing than HIMYM.
^This. HIMYM was a pretty standard American sitcom. Yeah, the mystery aspect was new, but the show mostly followed the formula set by so many other sitcoms that came before it. And Lily was a decent but ultimately forgettable sitcom character.
BtVS was an (imperfect) masterpiece of television and Willow's character evolved so radically over the course of the seven seasons that it seems ridiculous to even pose the question, OP.
Alyson Hannigan will always be Willow to me.