What techniques do these singers use?

[miranda]

I'm currently faced with the common dilemma of anyone who wants to start taking vocal lessons - effortless "diaphragm" singing vs. speech level singing. After reading about the technicalities of both, I still can't decide which I should start with! Of course the traditional classes would be easier on my pocket, but I've heard that SLS gives more "value for money" in a shorter time.

I thought if anyone could tell me a little more about the technique/styles the following singers use, I would have a clearer idea of what is what and what is not which will help me in my decision

Birdy

Jayesslee

Kina Grannis

Christina Grimmie

Christina Perri

Colbie Caillat

Who is singing "from the diaphragm" and who is "mixed"?