Who's a Better Referee? Teacher or Senior Colleague?

[akabir]

Hello, I am a potential PhD student for Fall, 2012. I am currently working as a Lecturer in a different University from where I did my B.S. and M.S. I have already decided on two of my teachers whom I'll ask for LOR. But I can't decide who should be the third one. Here are my choices:

Choice 1: One of my teachers who knows me pretty well. I have attended a couple of his courses. But he's an Assistant Professor, and I don't have any research experience with him.

Choice 2: A senior colleague who is a Professor. She has never taught me, and I don't have any research with her. But she can write about my teaching and my work, and the innovative things I have done in the department to improve the academic environment.

So who should i ask for an LOR? Will it be better if I have three teachers recommending me? Or two teachers and one senior colleague?