After Cole, every man that she got with just made her really annoying in my opinion. It just her and relationships just made her weaker as a character for me.
What I admire about Phoebe is her talent for psychology and I love her fighting skills. I like Prue's personality, her strength and also her fighting skills. As for Paige, I just love everything about her, she is brilliant.
I can't choose among Piper, Paige, or Prue. Phoebe is my least favorite sister. She got really annoying during the whole Cole drama... (After he became the Source.)