We have been on SB and SS three times each. All things being equal, we prefer Seabourn.
The experience just seems a bit fresher and we prefer the food. As well, we find the
Silversea butler system better in theory than in practice. That said, we go on cruises
for the destinations, not the perhaps stereotypical cruise experience of trivia games,
captain's parties, etc. The itinerary trumps all for us and we are happy to go on either line, as the differences are not that great.
Even cruises within the same line can differ markedly, depending on the length of the itinerary, time of year, and size of the ship. A 7 day summer cruise is going to be have a different tone than a 12 days cruise off season, the latter having a more mature crowd and some cruise "insiders" who have dozens of cruises under their belts.