Basically living in one or the other at the moment:

The Riverside is a very new one (2013). Nice modern but cool Scandinavian design, decent but a bit pricy restaurant and minibar. It is on the north side of the river on the Lindholmen science park areal. Not much to do there if you don't work here but it is a very short bus ride (10 minutes) to the central station and the buses go every couple of minutes - or you can take the ferry across the river.

The Scandinavia is older (I would say it saw the last major renovation in the mid 90s) but still well maintained and the restaurant (including minibar) is more reasonable priced. Also the location is great as it is like 3 minutes walking from the central station and downtown shopping areas.

Both are good choices for GOT but unless you work in Lindholmen or north of the river I would go for the Scandinavia. I have no idea where the Preem Refinery is, I only know the ST1 one, and that one is in fact north of the river and I guess the Riverside would be the more convenient location.

So, nicer one: Riverside, better located to see the city: The Scandinavia