I went on a HAC cruise with my wife when we were in our 30's as well. I tend to agree with the advice you have been given. If you don't see the activities on the cruise as being a high priority to you, and enjoy better food, HAC is likely a better choice. If, however, you are concerned that you may get on the cruise and decide you want a more active itinerary, then go with RCI. While you didn't bring up this option, if you want to go somewhere in between, Princess may be another option to consider.
Hope that helped.