To answer this question, it is useful to understand a little bit about the Multiphase Optimization Strategy (MOST) framework, developed by d3c collaborator Linda Collins at NYU’s cadio. The MOST framework describes three phases of an intervention optimization and evaluation research program—Preparation, Optimization, and Evaluation.  (Importantly, these are research phases (not intervention phases).)

A SMART is one type of experimental trial that can be conducted during the Optimization phase, where the objective is to identify the components of an adaptive intervention (e.g., decision points, tailoring variables, intervention options, decision rules) that lead to improved health or education outcomes.  

A confirmatory RCT is more appropriate in the Evaluation phase when the researcher is ready to evaluate the effectiveness of an already developed adaptive intervention.