I use all four of the Radisson in Helsinki regularly. The breakfasts are pretty much the same in all of them and are all you could want with a wide selection.
Hotel prices are generally quite high in Helsinki (compared with Stockholm) so the points rate doesn’t surprise me.
All are walkable to the centre. The Seaside is closest for the ferries and is usually the cheapest. It’s modern and some of the rooms have a sauna. Aleksanteri is smaller than the others and ‘cosiest’, and my favourite. The Royal was refitted a coupe of years ago and is nice, but completely lacking character. The Plaza is closest to the rail station and the grandest - but the rooms are just like all Radisson so the character stops at the door to your room.
I choose the hotel based on what I am doing in the evening, as all are pleasant and welcoming.