Are Belgrade or Novi Sad worth visiting?

25F, made the dumb decision to rent an Airbnb in Budapest for 6 weeks and then stay in hostels elsewhere during that time

So far I’ve been to Zagreb, Ljubljana, Vienna, Bratislava, Kosice and Presov . I’ve also taken a couple of day trips, to Lake Balaton and Eger in Hungary

I’m going to Prague soon for 3 nights but I’ll only have a bit over a week left after that.

I really loved what I saw of croatia and slovenia and frankly I’m a bit of a dork for communist history, so I thought Belgrade could be a good option, but I’m getting mixed opinions – mostly from people who have never been. I also love castles and saw they had one

I’m not a huge partier but will end up doing it inevitably. The big kicker is that it’s a 6 hour bus ride from budapest which is the longest non-train ride I’ll have taken. Then again, it’ll be air conditioned and can’t be worse than the circa 1970s non-AC compartment I took from Ljubljana to Budapest for what ended up being 9 hours, right?

Thanks!

Are Belgrade or Novi Sad worth visiting?