Among the many decisions to be made in their teaching practice, physics teachers must decide how to explain each particular phenomenon to students. This study explores student teachers' ("STs") decision-making process when presented with several explanations of a physical phenomenon that might be used for teaching purposes. During individual interviews, seven "STs" were offered three different explanations of how a tensiometer works, all with an accurate conclusion. They were also supplied with a grid of criteria for critical analysis. Following in-depth critical analysis of the three explanations in close interaction with the interviewer, each "ST" was asked to specify the criteria for their choice of explanation, for themselves and for university students. Even after stressing that they valued consistency, some teachers opted for an explanation for students that they had just described as inconsistent and/or incomplete. More specifically, their comments revealed conflicting ideas about the need for consistency and the various forms of simplicity or incompleteness in a given explanation. The results invite more explicit consideration of the complex roles of simplicity or incompleteness in explanations and the importance of this type of interaction during teacher preparation.