Hi. The student and the faculty interviews count equally. So it's important.
I think the interview portion of the application comprises roughly 15% in the admissions point system. So each interiewer's evaluation of you on a scale of 15pts is worth 7.5% overall. Hope this helps.
I liked my student interviewer, but my faculty interviewer was a bit strange. She asked me about my family life, something that I consider to be personal.