For whats its worth, I have stayed at the Raddison Blu Seaside (not my style normally but it was a group thing and I did upgrade myself to a suite complete in-room sauna). It is a very nice hotel but appears to be rather out of the way. However, the Tram line ends right in front of the hotel so it is very easy and fast 5 mins to access the town centre.

I would not be too concerned about hotel locations as the trams are very good and you can get a pass for the length of your stay. You do need to make sure the Tram lines are handy for the location.

You may wish to consider location only if you intend to party late at night as the trams are not 24 hours. Taxis are very expensive in Helsinki, as is food and almost anything else.

Love the reindeer meat but could not bring myself to try bear.