As far as Buffy's attitude toward Andrew as opposed to Spike, if you look more closely, you might just see more similarities than differences. Both started out as Buffy's "arch nemeses-es," both were the least respected member of their respective gang, both were thieves and murderers, and both were allowed through their actions and attitude to redeem themselves and become members of the team, though not part of the Scoobies' inner circle (actually, in this, Andrew actually was accepted more than Spike was). The greatest difference between the two is degree and length of "bad-ness." Spike was bad for a century and a half, Andrew was bad for a season. Spike became one of the good guys over the course of three seasons, Andrew only took about three episodes. Vampire and criminal mastermind parallel each other quite well if the time factor is eliminated. (But, PLEASE, GOD, let's not have a Buffy/Andrew equivalent of "Smashed." Andrew/Xander, Andrew/Dawn, or Andrew/Rona, maybe, but no Andrew/Buffy!)