Their larger ships which they are still building new ships are about the size of Voyager Class at about 130,000 tons. It is expected that they will share the Discovery Class builds. They have smaller ships the same size and age as Radiance Class. Matter of fact those share the same hull as Celebrity Millennium Class. Celebrity also has a later class than Millennium , Solstice Class about 120,000 tons which are my favorite Celebrity ships.
Silversea is expensive and an option for me but I have never booked. I prefer non RCG ships in that category. One thing about more expensive cruise lines is that on many the perks you are fighting for in the loyalty program are included.