Professional development (PD) is one way to maintain or increase teacher effectiveness in any number of domains. However, PD comes in many formats and with a wide range of evidence on its effectiveness -- both of which can shape teachers' perspectives of the PD even before they participate. The purpose of this research was to examine how elementary and secondary teachers evaluate different types of PD based on their content and delivery format and on their supporting evidence. Teachers were quasi-randomly assigned to read one of four vignettes describing a fictitious PD programme claiming to improve student motivation. There were four PD conditions resulting from crossing two programmes (conventional vs. unconventional) and two types of evidence (experimental vs. qualitative). Teachers (n = 539) evaluated one of the four PD options in terms of its quality and how efficacious they thought it would be in helping them motivate students. On both outcomes, elementary teachers preferred PD supported by qualitative evidence over experimental; whereas, the opposite was found for secondary teachers. There were no preferences based on conventionality. We discuss the implications of these results in terms of making information accessible to teachers and in terms of addressing teachers' research literacy.