UCI institute of math behavioral science vs. UCSB Econ vs. UCR Management

[mochimochi]

I've been admitted to above three schools. All are Ph.D. programs.

UC Santa Barbara Economics Ph.D. has good ranks and beautiful campus, but I am afraid economics phd will be too challenging for me and I might fail the qualifying exam.

UC Riverside Business school Ph.D. offers only 4-year funding. They said fifth year is not guaranteed, but they will be able to work something out. Since the B-school is new, I will be able to receive support and attention from faculty. Job prospect looks good given that it's b-school, but I am not sure how overall ranking of UC Riverside will affect. 

UC Irvine Institute of Mathematical Behavioral Science offers 5-year funding. Job placement looks good, coursework seem hard but there's also flexibility in choosing courses/fields.Since this is not a typical ph.d. program, not sure what questions I need to ask myself before make final decision. Do any of you know about this research institute? 

Which of these three options should I choose? I am not sure of whom I will work with, or which topic I will study yet. I also weigh distance from the city(los angeles), while irvine is the closest, riverside and then santa barbara is the farthest. I am really lost.