They all became the largest ships in their respective cruise line (I think you meant Silver Spirit) and added more dining choices as the cruise lines began in earnest to move away from traditional dining as the featured meal of the evening. Entertainment also moved forward in most cases, with more innovative shows and technology. But with the added number of passengers per ship, I think there has also been an increase in the anonymity of the passengers. Both groups of ships have made it easier to go on a cruise and not meet anybody new.
There is also a sweet spot in ship size and passenger loading among the mainstream lines listed, which Norwegian Epic first introduced and then the others have more or less followed with the four ships in the second list. This is not favorable in my view, since they are pretty dense ships with lots of people and less open deck space and smaller public rooms.
Within the past few months I've cruised on both the Royal Princess and the Norwegian Getaway and found both to have a similar feel to them. Cluttered is a good word for it. I liked Getaway a lot more though, simply because the crew was more engaging and fun, and the entertainment was on a clearly higher level.