Ponto-Caspian dreissenids are notorious freshwater invaders. Recently, there have been widespread observations of a dominance shift from the first invader, Dreissena polymorpha, to its successor, Dreissena bugensis. This study assessed to what degree this could be explained by their attachment strength, attachment rate and detachment location, taking into account the shell size, age, byssus thread morphology and population composition. During a field experiment, fouling plates were deployed in the Rhine-Meuse delta in the Netherlands. During a laboratory experiment, the attachment strength was measured after 7 days in 60 litre non-aerated freshwater tanks. The shell size and attachment strength were positively correlated. In natural environments, this led to a higher attachment strength for D. bugensis compared to D. polymorpha individuals of the same age. Dreissena bugensis grows faster and larger than D. polymorpha does. Comparing individuals of the same age, therefore, leads to more realistic results relative to comparisons between individuals of the same size. Additionally, D. bugensis had a significantly lower attachment rate and a thicker and higher number of byssal threads than D. polymorpha. Moreover, D. bugensis had a significantly higher attachment rate in light environments compared to dark conditions, while there was no effect found for D. polymorpha. We could conclude that D. bugensis probably spends more time searching for the optimal habitat. Once settled, its higher attachment strength gives it an advantage over D. polymorpha when it comes to withstanding currents and predators. These characteristics could contribute to the ongoing dominance shift.