The Waterfront is only a few years old, and so it's rooms are more contemporary and in better condition overall than the rooms at the Viking or Strand Radisson hotels here. I still tend to go for the Strand over the Waterfront; or I pick the Waterfront over the Viking if doing Radisson and not staying at the Strand property. If the weather was lousy, the Viking is indeed as convenient as it can get when using public transit of sorts.
More often than doing Radisson hotels in Stockholm, I now mostly use Choice hotels or SPG/Design Hotels in Stockholm when it comes to using points. That's even as there seems to be at least marginally better welcomes at Radisson hotels here than at Choice hotels. However the redemption values Choice has in Stockholm are very good, something that doesn't seem to be as generally true for the Radisson Blus in the city center area. But if using the employee friend and family rate, the Waterfront tends to have much better availability than the other Rads.