+pillz because of the no minimum but really they are only great used in mono-clan or teamed with Ula Watu, maybe Bangers. -pillz is best against the same but can also force your opponent to use pillz rashly to avoid losing them to the ability. Makes for a good bluff card.
When you plus pillz, you can waste a bunch of pills just so you get the victory and in the end you can get a bunch of them back. When its minus pillz you have a bigger chance of losing and not having the effect come into play.