Bioelectrochemical systems need an anode highly enriched in exoelectrogenic bacteria for an optimal performance. Among all possible operational parameters for efficient anodic enrichment, the role of external resistance in microbial fuel cell (MFC) has gained a lot of interest since the external resistance indirectly poises an anode potential, a key parameter in bioelectrochemical systems that determines the energy gain for the bacteria, and thus enhances the growth of different anodic microbial populations and determines the biofilm morphology. Thus, this work aims at investigating and discussing whether bioanodes selected at different external resistances under MFC operation present different responses under MEC operation. The results show that a better performance in MEC mode (i.e. higher current intensity and higher H2 production rate) is obtained with an anode previously inoculated under low external resistance (12 Ω) in MFC mode. qPCR confirmed that a low external resistance provides an MFC anodic biofilm with the highest content of Geobacter, because it allows higher current intensity, which is correlated to exoelectrogenic activity. High resistances as 1000 Ω are not recommended because Geobacter growth is more limited (lower current intensity), which leads to a slower start-up under MEC operation.