Niche protection comes up a lot in those kind of comparisons, too. Many groups (but not all) are okay when the combat specialist does his thing, similarly when the social specialist does her thing, etc. But when two people occupy a similar niche, like both being melee attackers or both being a persuasive charmer, then the players can start eyeballing each other if one is doing MARKEDLY better than the other.
It can get more pronounced when the "toe stepping" comes from an unexpected place / triggers mental dissonance, like a Fighter comparing themselves to a Sorcerer going nova in D&D. Or when they have parity in one category (say, damage), but one of them has oodles of additional tools like being able to fly around, open portals to other planes, etc.