We've been on Millennium, Solstice and Edge class ships and would say the Solstice ones have the same vibe as Royal class ships.
Entertainment is better I think on Princess. There just seems to be more going on. I miss Morano's however as Sabatini's isn't as good.
MUTS is great, but Celebrity have TV screens too. Just not as big!
Like many have said, you will not be disappointed with the switch to Princess.