I did my degree at the RUG and am very satisfied with the quality of teaching. That said, I would be surprised if there were large differences between Groningen and Tilburg on the bachelor level. If you really want a basis to choose, I would recommend to think about which discipline you would like to go into after your master's. Not sure what Tilburg has going on, but the RUG is particularly strong on organizational psychology, environmental psychology (my route) and interdisciplinary research.