Crystal has "themes" on many of its cruises. The food and wine theme generally means a noted chef and a wine expert will be on board for a series of cooking demonstrations and wine tastings -- free of charge, of course.
Crystal in the evening is a more dressy line. On an average 12 day cruise there are 3 formal nights, 3 informal nights, and 6 casual nights. 90% of the men wear tuxes on formal nights with the women wearing either long or short gowns or dressy pant suits. After 6 p.m. in the public areas of the ship, everyone must conform to that night's dress code. For informal nights, a jacket and slacks are required for men but ties are optional. Women wear nice dresses or pant suits. Casual is "country club casual" -- for men, slacks and sport shirts are generally worn and women wear sporty pant suits.
Judith summed up the dress on Crystal very nicely. Crystal is probably the most formal of all the lines in the evenings.
Seabourn is a very different type of cruise ship from Crystal. They are very small ships and therefore don't offer all the activities of Crystal. But their food and service is the best of any line I've been on. I didn't care for Radisson at all. Their food and service is a notch below both Crystal and Seabourn. Their cabins are the largest of any cruise line, and they aren't as dressy as Seabourn or Crystal. I found the service on Radisson to be quite lacking also.