It is impossible to make an objective statement of who "best understood" the adult learner and it is fruitless to express a dogmatic opinion on who did. The useful approach in evaluation is to ask "Whose approach is most useful in various situations adult learners find themselves?"
It is also important to be aware that the answer may change with changing situations, for example, classroom versus distance online learning or expanding a present knowledge base versus acquiring new knowledge.
Rogers emphasized "realness" or validity to experience. Dewey's Constructivism emphasized the contribution of 'sociocultural" participation as in group learning.