I have 100+ nights on both Regent and SilverSea. Have also done Seabourne, Norwegian, and Royal Caribbean though it has been a while for Norwegian and Royal Caribbean.
I would put Regent at the top of the list, but the price point probably reflects that, too. I also love Seabourne. It is a bit more casual than Regent, but the ships are beautiful and the really have a nice feel to them.
I have spent a lot of time on SilverSea, but I feel like their dining is sub-par compared to Regent and Seabourne. It would take something extraordinary to get me back on SilverSea at this pointl.
The food on Regent is, in my opinion, exceptional. First time I have ever had a really good steak on a cruise ship was in Regent's Prime 7 restaurant. I lived in Chicago for 20+ years and have a pretty high standard for steaks, and I was honestly a bit shocked at how good the steaks were on Regent. Other food choices are also outstanding.
All three of these lines are going to generally be an older crowd. I am 57 and my wife and I are usually among the youngest on the cruise, but that also means that they are relatively quiet and relaxing. Other than grandma face-timing with the grandkids, the pool deck is usually a great place to relax, read, have a drink, take a nap, or whatever.
We are not real big on the shows, but have been known to close the casino down on occasion. Actually got a ride home from the casino one night, but that is another story altogether.