I do believe you will enjoy NCL. I have cruised both NCL and Carnival and overall I enjoy NCL more. The main reason is "Freestyle Cruising".
I love being able to eat where, when and with who I want. I have never had a problem getting a reservation in a specialty restaurant. The video screens that show the restaurant availability are great and if you are flexible there is always one that is available.
Add $100 - $150 to your cruise budget to enjoy all of the restaurants and you will have some of the best food at sea.
You will also be able to stay in your cabin on the last day. Have breakfast in the dining room or the buffet and leave when your color is called or when you want. On my last two Carnival cruises everything was great until the last day when I felt like a cow being herded off the ship.
I would never limit myself to one cruise line just to obtain Platinum status. This reason puts limits on where and when you want to cruise. I have elite status only on Celebrity and it is about sixth on the list when I look for a cruise.