I've never sailed with Seabourne, so cannot provide any comparison, but the Silver Wind is one of my favorite ships. I did Silversea's "Signature Seychelles" on the Silver Whisper a few years ago sailing from Mombasa to Mombasa with port calls in Mahe, Praslin and La Digue. It was my first cruise aboard one of the newer (and slightly larger) vessels and I didn't think it had the same level of intimacy as the Cloud and Wind. Nothing "major" but just a vague feeling of things not being quite up to the same level. That was the just personal impression I received and certainly not enough to deter me from booking again - I'll be on the Shadow next month. The bathrooms on the newer ships, however, are just wonderful!
I really enjoyed the Seychelles. You won't find a lot of non-stop activities on the islands as they are most known for their beauty and natural resources, but if you appreciate the opportunity to actually relax while on vacation, you'll love them. My favorites were a tie between visiting Moyenne Island (privately owned by ex-journalist Brendan Grimshaw and reportedly home to hidden pirate's treasure) and just soaking up Grande Anse on Praslin (one of the most photographed beaches in the world). If you're interested in guidebooks, I had bought a copy of the Michelin Neos guide to the Seychelles which I thought was one of the best I've ever read.
I don't know if Silversea is offering a pre or post cruise safari with your cruise, but the Micato safari's are also excellent. I did the pre-cruise option which included sights in and around Nairobi, Amboseli National Park and the Masai Mara. My only regret was that I didn't spring for the "Ultimate Safari" option, thinking only of the upgraded accomodations, which didn't matter much to me. What I didn't consider was that there were about thirty or forty people in the "regular" safari with me whereas there were six people total in the ultimate group. I didn't think crowding was an issue or anything; everything was handled perfectly, but I think I really would have appreciated the smaller group.
Hi I use to be a Seabourn fan myself. I have now cruised 6 times with sliversea and would say it would take alot to change me back. Wind & Cloud are the companies two baby ships and are similar to Ledgend but with balconies. The seychells are a fantastic location to visit on any small ship. Im sure you will have a fantastic time. Silversea has much better wine cellar but Seabourn has better water sports facilities and probably a slightly younger passenger age group. Hopes this helps.