Assistant Prof of Full?

[prospectclin]

I'm applying to Clinical Psychology and many of the schools I'm applying to only require 2 references. I have an existing Master's in another field and my first reference will be my Master's supervisor. For my second reference - Is it better to ask an assistant prof who I have a very close relationship w/ for a reference? Or is it better to ask a full professor who is the head of a department and served as one of my thesis advisors?

[fuzzylogician]

Get the stronger letter. 

[prospectclin]

thanks for your reply!