It's like being forced to choose a favorite child when both are mewling and puking, squawking for attention. Given a limited amount of time, the reading, reference checking, and writing slide. Nobody but me suffers in the short term if I deviate from my dissertation schedule, but it's torturous and unethical to arrive at class unprepared. So I'll grade one more set of papers, thinking with petulant longing of my lonesome, overheated study carrel. With increasing specialization and narrower fields of expertise, publications by professors often seem to be more and more removed from the fundamentals of their fields.
Teaching involves explaining the basic, the general, the introductory.
Either you're breaking new ground in your research, or you're explaining to others where you've been through teaching. As a consequence of this, the hierarchy of higher learning generally ranks the research university over the teaching college, a leveraging that seems axiomatically to validate research over teaching, to see the latter as an imposition on the former. Even if I may not like it this way, the tenure system and the opinions of colleagues do seem to function with these assumptions. Often I let my mind grumble this way about the polar pulls of teaching and research. But then three years of teaching first-year writing force me to recognize the logical fallacy, the false analogy.