The central tension in those stories typically pits a deep, established emotional bond against a new, destabilizing attraction. It's less about which person is objectively 'better' and more about the protagonist confronting conflicting versions of themselves—who they've been versus who they might become. The external love triangle is just the stage; the real drama is internal, a crisis of identity and values.
I just finished one where the female lead was engaged to a stable, kind childhood friend, but then she kept running into this chaotic artist who challenged everything she thought she wanted. The conflict wasn't really about the guys; it was her fighting her own desire for a predictable, safe life against this terrifying pull toward something unpredictable. The book smartly made both choices feel like genuine loss, which is what makes the genre work when it's done well.
That internal war is what I find most compelling, even when the execution falters. You're watching someone tear themselves in two, and the resolution, whether satisfying or frustrating, always reveals what the author truly values—security or passion, duty or freedom.