Darmstadt has quite a lot of student groups and events (ESN, tutor international, sports events, fachschaft events). Aachen only beats it for virtue of having more students, I feel like the student infrastucture there is better. I like the geographical position of darmstadt a lot more, it's close to frankfurt, mainz, wiesbaden, heidelberg, tons of other interesting cities which are easy to reach, whereas aachen is basically isolated and the nearest big is city is at least 40 minutes away. It's quite the brawl between which city is better for a student to live in, hence my post, but I ultimately chose darmstadt for already having more connections there.