Operational experience as well as safety analyses provide strong evidence for the fact that human performance is critical to the safety of complex systems. Accordingly, significant efforts have and continue to be applied to enhance human performance and reduce the potential for human errors. In this regard, full-scope simulators are an especially useful instrument to observe the performance of human operators, in particular, in hypothetical accidents. For such observations, it is indispensable to specify the information that should be collected or measured, in order to be able to analyze and understand the various influences on human performance and their impacts. In specifying this information, the experiences of Human Reliability Analysis (HRA) and Human Factors (HF) engineering are relevant because one of their common aims is to support the safe operation of human-technical systems by reducing the human error potential. In this work, guidance documents of HRA and HF engineering were reviewed in order to compile the types of information recognized as crucial influences on human performance. This paper compares these sets of factors, discusses the differences, and examines how these may be combined, in particular at the level of the measures used for observation and analysis.