KU Leuven is a great university offering a wide variety of courses. The quality of education is very good and tuition costs are low (at least for EU students). The university has a good reputation and is known to be the most difficult university in Belgium.
Leuven is a nice city, but be aware that it is quite small. I have been here for three years now and wouldn’t want to stay much longer. However, it’s not too boring as almost half of the population are students. There is also a campus in Brussels, so if you enjoy living in a bigger city you could go there.
Overall, I would certainly recommend going to KU Leuven.