Although cabins not near as large as on Navigator or Voyager, the Promenade makes up for it. Stars Lounge, although rarely used, means private parties don't take over regular lounges. She is a little larger than Voyager with a better ride.
Marc....I agree. Too bad none of those lovely lounges on top of the ships -- on any of the luxury vessels -- are ever used. I've visited one late at night and the only person there was a harpist, playing to an empty room.
The Diamond. Whilst it is, regrettably, no longer in service to Regent, it was the only cruise ship I passed beneath the hull in a tender! This whilst off Dubrovnik. Shame she went it felt like a private yacht, the crew from the Captain down were so friendly and helpful. A sad loss.
I agree on the Mariner as my favorite RSSC ship, for all the reasons stated above, plus another reason. We have cruised all the current RSSC ships (plus the departed Diamond). The Mariner is the only ship remaining in the RSSC fleet on which we have not encountered a vibration problem somewhere on the ship. Of course, ships (like all mechanical things) all have some vibrations under some conditions. When I say "vibration problem", I mean a constant and severe vibration on a portion of a ship anytime the ship is underway at cruising speed. The Mariner does not have any such problem, to my observation. The rest of the current RSSC fleet does.
I have cruised on the Paul Gauguin, Diamond and Navigator and several other "High End" cruise ships and by far without a doubt the most fantastic cruise experiences we have had have been on the Paul Gauguin and the Diamond................! Just my thoughts as I have sort of been there done that with cruising around over all the years.
Well, if you include itinerary and included activities in the definition of "favorite ship" my answer then changes from the Mariner to the Paul Gauguin. The itinerary and activities override the fact that the rooms on the PG are much smaller, IMO.