Must admit, I'm not a fan of the Radisson Blu hotels in Copenhagen at all, nor their locations (although the Royal is at least near the station).

The Rad Scandinavia is in kind of nothing area. The walk to more interesting parts of town is OK, but you're could be facing howling cold winds walking over Langebro in December (I've cycled over there in -15C, I don't recommend it!)

The metro system is quick and efficient, with little driverless trains running every 5-10 minutes. It would be quick to get you up towards Kongens Nytorv (for Nyhavn) and that part of town. Towards the station and Tivoli, you're probably better off on the bus - they're pretty easy to figure out. If you're planning on taking the S-Tog out to Ballerup (don't know your arrangements - taxis are ruinously expensive, though), then the main station (Kobenhavn H) is the hub, but there are also stops on a loop round the city centre.

Personally, I tend to prefer to stay more in the centre in Copenhagen, and haven't found a chain that gives me the right balance of location, consistent price and quality, so I tend to stay at a variety of boutique hotels instead (and the odd local chain). But I do also tend to cycle around there - although if this isn't something you do regularly, December in Copenhagen is not the place to start.

The good news is that it's a fantastic city for just wandering around. And, to be fair the Scandinavia, you can head both towards Tivoli and through Christianshavn towards Kongens Nytorv, etc (there's little of interest in that part of Amager otherwise).