Yes, the "party ship" atmosphere on Carnival is a myth. All shorter cruises will feel like party ships compared to 7 day and longer itineraries, that goes for Royal, Carnival, and NCL.

Carnival puts out a product that is more or less equivalent to NCL and Royal. The primary difference with Royal is in the ships. IMHO the ship amenities aren't worth the steep premium to sail Royal. IMHO Carnival and NCL are almost exactly identical, though we're big fans of Freestyle. Carnival's anytime dining plan works well too, though, and the greater variety of ships and itineraries out of Florida makes Carnival our line of choice. Carnival also has a better kids' program than NCL.