We did not do any Princess excursions; even compared to other Princess cruises we have taken in the past, the prices were ridiculous. We did hop-on-hop-off in Oslo and Helsinki, went on our own in Aarhus, Kiel ( Berlin was cancelled because the port was closed due to wind), and Tallinn, and used SPB tours in St Petetsburg and Stockholm.
We went with SPB instead of Alla or another tour because the owner Vika was the only one who responded to my concerns/questions personnally; Alla send me a form letter and I never heard from them again.
We had no problem getting off the ship or through Russian immigration despite what Princess states in their literature; a passport and tour ticket was all we needed. The tour covered the same attractions as the Princess tour but at half the price. We moved right along but were never rushed. Vika was our guide; she retained her sense of calm even when our group was split up on the ferry to Peterhof by another tour group; Another SPB guide, Svetlana, took over temporarily until we were reunited.
We did a hop-on-hop-off. We were stuck in the upper deck on a rainy day so my opinion is colored by that. There were only 3 sights I really wanted to see. The Vigeland sculpture park, the Viking Ship Museum, and the Kon-Tiki museum. We skipped the sculpture park as it was raining we were already soaked. We did stop at the 2 ship museums and were impressed.
Again rain. We didn't make it to Den Gamly By but spent most of our short time there at the ARoS museum. Fascinating place, both the building and the art. Lots of cutting-edge modern art.
We went on our own and enjoyed walking through the old town. We also browsed a modern mall across from the old town I was told that there were free tours but I never found them - maybe the rain kept them away.
We did a hop-on-hop-off and caught most of the main sights. We walked through downtown Helsinki. Stockmann's department store has a grocery in the basement - fun place to see what people might eat in Helsinki.