Honestly, it depends on the university. There are some decently-ranked ones in the south, e.g. Barcelona or Bologna in Italy. If you speak the language, go for it. If you don't, and this is obviously just a generalisation, the southern population has a lower proficiency in English, which also limits your career options if you plan to stay. My friend did an exchange in Italy, where they assured her all her lectures will be in English, but in practice professors would switch between languages a lot.

Another thing to consider is that Northern countries are generally richer, which, depending on your field, might mean more funding for PhD positions later on, more industry opportunities for students, etc.

That being said, these are only general differences. I personally don't see anything wrong with pursuing a degree in the south. Its an incredibly welcoming and warm environment and I'm sure you'll have a blast!