This paper compares the essential divertor transport features of the poloidal divertor, which is well developed for tokamaks, and the non-axisymmetric divertors currently investigated on helical devices. It aims at surveying the fundamental similarities and differences in divertor concept and geometry, and their consequences on the functioning of a divertor. In particular, the importance of various transport terms governing axisymmetric and helical scrape-off layers (SOLs) is examined, with special attention being paid to energy, momentum and impurity transport. Tokamak and stellarator SOLs are compared by identifying key geometric parameters through which the governing physics can be illustrated by simple models and estimates. More quantitative assessments rely nevertheless on the modelling using the EMC3-EIRENE code. Most of the theoretical results are discussed in conjunction with experimental observations.