I would say that the Nikāyas and Āgamas give us a “historical-realistic perspective” on the Buddha, while the Mahāyāna sūtras give us a “cosmic-metaphysical perspective.”

Bhikkhu Bodhi explores the Bodhisattva ideal from the perspective of the both the Theravada and Mahayana, with a brief summary of its history. An excellent introduction to this vital topic.