I frequently come across PhD dissertations that have spawned multiple journal papers, either while the author was working towards their Ph.D. or after completion. My field is not one with "stapler" dissertations that merely collate a number of papers, so there are often differences between the details of the paper and those of the dissertation.
However, often there are claims/statements/arguments that are present in both sources, so which should I prefer to reference? Should I cite the earlier reference? The later one? Or are there other issues I should consider?