I think in the social choice literature, people almost always mean preference utilitarianism when they say “utilitarianism”, whereas in the philosophical/ethics literature people are more likely to mean hedonic utilitarianism. I think the reason for this is that in the social choice and somewhat adjacent game (and decision) theory literature, utility functions have a fairly solid foundation as a representation of preferences of rational agents. (For example, Harsanyi’s “[preference] utilitarian theorem” paper and Nash’s paper on the Nash bargaining solution make very explicit reference to this foundation.) Whereas there is no solid foundation for numeric hedonic welfare (at least not in this literature, but also not elsewhere as far as I know).
I think in the social choice literature, people almost always mean preference utilitarianism when they say “utilitarianism”, whereas in the philosophical/ethics literature people are more likely to mean hedonic utilitarianism. I think the reason for this is that in the social choice and somewhat adjacent game (and decision) theory literature, utility functions have a fairly solid foundation as a representation of preferences of rational agents. (For example, Harsanyi’s “[preference] utilitarian theorem” paper and Nash’s paper on the Nash bargaining solution make very explicit reference to this foundation.) Whereas there is no solid foundation for numeric hedonic welfare (at least not in this literature, but also not elsewhere as far as I know).