I have stayed at both Pension Anna and the Holiday Palace in the past.
If you want to experience a 1970s Hilton go for the Holiday Palace as it was once a Hilton. Some of the rooms may be a little high for decent photos from the balcony.
Pension Anna is definitely close to the action so it would be worth making a call to the number to see if it is still in business as I was last there in 2008.
At the time of my visits the Royal was in a poor state of repair with the swimming pool built into the hillside looking like it would burst like the Mohne Dam any minute. However I understand some significant refurbishment has taken place since then.