It's likely a matter of taste, and as beautiful as the Regal Princess is, it's just too big. Seeing the sights of the Baltics was a spectacular adventure, one easily taken because of Princess. If you can afford to go with a smaller liner, your vacation will be that much more enjoyable.
We stayed and extra day in Copenhagen on the return trip home. It was lovely. The Scandic Hotel was a great surprise.
Our experience with such a large floating hotel was a little less than perfect. The day we were to disembark in St. Petersburg we were held by Princess crew from getting off to meet our tour. The crowd that had waited patiently for nearly 2 hours became hostile and with Princess not wanting to back their customers, a free for all nearly broke out!