LEED Canada for Existing Buildings: Operations and Maintenance (LEED Canada EB:O&M) and Building Owners and Managers Association's Building Environmental Standards (BOMA BESt) are complex green rating systems that offer owners, managers, consultants, and tenants distinct value propositions for existing buildings. Upon close examination, significant variations between the systems are evident in certification process, cost, rigor, engagement, marketing, accessibility, transparency, management, and program philosophy. Despite the many differences between the systems, they are often seen to be complementary programs and are sometimes used in tandem for the same building. This paper reports on a survey of the industry perceptions of the value and strengths of the LEED Canada EB:O&M and BOMA BESt rating systems with respect to the above criteria. As a result of the fundamentally different nature of the programs, preferences for LEED Canada EB:O&M and BOMA BESt are determined by stakeholder values and the programs are used for a variety of reasons.