Numerous people have stated that the two are very similar. In fact, there are active threads where this is being discussed.
One difference is that Silversea is all-inclusive (alcohol included all of the time). While I have not been on Silversea yet, I understand from the wonderful people on this board that you cannot go wrong.
🚢 Cruise with your favorite Keene Luxury Travel Staff Member! 💰 5% KLT Reward plus Shipboard Credit available (amount varies per voyage)! 💲 Offering Enhanced KLT Rewards on voyages hosted by Ngaire & Clay!