This is in regards to using 2 or more different types of lavalier brands for the same shot or interview. The ones I currently own are Sanken Cos-11d and DPA 4071 with the higher presence boost.
This is taken from a live hangout I did on Youtube:
I typically don't tend to mix different brands of lavs on the same shot unless certain circumstances mean that I can't get the sound that I like. Generally I would use Sankens and then if someone has a really deep voice or I had to place the lav nearer to the throat then I would normally because of costumes then having the option of a mic with a presence boost would give me more clarity.