Intro/extraversion difference: there's less "getting in each other's way" with respect to initiative for extroverts, and somebody will actually take the initiative for introverts.
Shared rationality: similar "rhythms", rationals may perceive irrationals as lackadaisical or flighty, irrationals may perceive rationals as uptight.
Overall, your strengths are more opposite too, so you more easily divide up the world into your domains.
Functionally, the mobilizing function can be quite stubborn which can lead to friction with the leading function of your activator. Less so with the creative function which is very flexible.