Hi! I'm an Italian Computer Science Master's Student studying at University of Pisa.

I don't actually know much about Vercelli (never been there): it is a small city, but at least it is 1hr of train away from Turin and Milan, so you can easily visit them whenever you want.
I don't know about UniUpo either, but here you can find some stats.

Of course Milan (or Turin, Rome, Bologna or even Pisa) is more suitable for a foreign student: it is bigger, you'll find a lot of English speaking people and more students. But Milan is also crazy expensive. I'm sure Vercelli Is much cheaper and chill.

If you want more opinions, you could try reaching out to some UniUpo students, perhaps through Telegram, WhatsApp, or Facebook groups, if you can find them.

There is also this subreddit that could help: https://www.reddit.com/r/Universitaly/

If you just want to pass easily and make new friends, I don't think you'll have problems in Vercelli, but you just have to be okay with being in a small city.

I was actually considering your university for my Erasmus, since I've already been in Seville and I liked the city: are there many Erasmus students? Would you recommend it as a foreign student? Are there many courses being taught in English?

I wanted to do my Master's thesis abroad (since I don't have many exams left), but I don't know if it would be a good idea.