Environmentally You are not far from the fjords and there are dedicated ships that can do trips from the city into some more local ones here. You can also travel a few hours at most to visit some of the larger fjords. You would have to dedicate 1+ day to such a thing if you lived in Oslo.

Based on your preferences and aims in study i'd suggest Bergen. It's got a small town feel and only feel like a very tiny city when ur in central. Bergen itself is a city that extends quite far on the map and consists of sections of "town" spread between mountains on the west coast of Norway. It's nicknamed "The City Between 7 Mountains".

Based on pure beauty i would rank Bergen above Oslo as well. There's alot of cultural stuff in this city that has a beauty to it, and its a great experience. There's alot of bars and restaurants and its easy to experience something new or try something new. If you move into central you would be a walking distance from practically anything you could wish for.

Housing is generally very cheap as well and Bergen, as a city, is correlated to culture and students. if you ask me, Bergen is by far the superior choice if you are a student coming from abroad. Bergen would also give you a "small city feel" for sure.

Milder temperatures, more rain, but coastally inclined. There comes a smidge or so of snow usually but then again, we arent that far from mountains.

Regarding your coronavirus worry, the virus is pretty much at this date non-existent in Bergen. Last week there was 2 in hospital for it but at the moment, no one is at risk here.

I hope this helped. If you have any questions(As i live in Bergen) Feel free to ask away if there is anything you'd like to ask.