I've been in suites and regular balcony cabins on Carnival, NCL and Royal Caribbean. All you are getting is a larger cabin. If you need the extra space - great. If not, you have paid for something you don't need.
Carnival doesn't offer any perks for its suites beyond priority check in. However, even that perk gets watered down because anyone with ten or more cruises with Carnival gets the same perk.
Royal Caribbean doesn't offer much of a perk with its suites. If you are on a ship with an ice rink you get the ice show tickets handed to you. The tickets are free to anyone, so you just don't have to wait in line. Sometimes you'll find an extra "treat" in your cabin (fruit for example). The same fruit is free in the Windjammer. There are some reserves seats, but unless all the other seats are taken, big deal. The seats are free for everyone else. You get priority check in. However, the check in process is fairly efficient and it turns out that is not much of a perk. You get access to the Concierge Lounge. Some people think this is a big deal. If you think it is - great. I didn't think it was all the big of a deal.
NCL does treat its suite guests like kings and queens. However, you pay a lot more for it. Lets take a look at a standard balcony on the NCL Jewel going to the Caribbean in mid March. The most expensive balcony cabin is $969 per person. The cabin is 167 sq. ft. with a 38 sq. ft. balcony. The lest expensive full suite (you have to be in a full suite to get the special treatment) is $1,799 per person, or $1,660 more for the week. In return you get a cabin that is 287 sq. ft. with a 54 sq. ft. balcony and special treatment. So, if you don't need the extra room, is the special treatment worth it? Again, you'll get treats (some available to all free - some not), a concierge and butler (both of whom you will be expected to tip extra for - so they are not free) and some special treatment (priority tender tickets and priority reservations - NCL is Freestyle, so for some meals reservations are necessary). It is up to you if this is worth the extra cost. I didn't think so.