It comes down to state funding. Funding drives the student/faculty ratio, library size, facilities, and 'per student funding,' which US News uses to rank schools.
UB Law is a part of the University of Maryland System (USM). However, we are funded at 45% the per student level as UM Law School, while day students pay nearly the same tuition and PT students pay about 3k per year more in tuition than UM Law. HOwever, you can register for classes at UM law through the UB registrar since we are part of the same 'school system.'