Haven't tried Chops, but you can get seconds at Portofino. HOWEVER, remember that the portions are quite large (unlike the dining room) and even without having all the courses offered, I could barely stuff down dessert (but they will pack it up for you to take back to your cabin if you want).
We ate at Chops and it was worth every penny. As someone else mentioned, the portions are a bit larger than the dining room. If you have ever eaten at Ruth's Chris, it is similar quality ...
We didn't consider asking for seconds because the food was so good that we were very satisfied after warm rolls, salad, dinner with starch and vegetables and dessert. The wine list was different from the dining room, and some of the wines by the glass were quite expensive, but I figured it was all part of the experience.
RCCI Mariner of the Seas - Western Caribbean - March 2006
Next up ... Mariner of the Seas - Eastern Caribbean - September 2006
We ate at Chops when we were on the Mariner last summer and the food was fantastic. we are going on the Mariner again this summer and Chops it on our priority list of places to eat. The food quality is excellent and the portions are very generous. Where else can you go for a top notch steak dinner for $20 a person (Outback doesn's count)
MARINER OF THE SEAS-JULY 2006
MONARCH OF THE SEAS-DECEMBER 2005
MARINER OF THE SEAS-JULY 2005
MONARCH OF THE SEAS-AUGUST 2004