Sounds like you have a couple ways to go. The full refund with take more work. However, if that is what you want you could fight for that.
Me personally I would have them switch the booking to another cruise like the equinox. Get a reservation number and check to make certain the booking is good. But I love to cruise so the cruise is worth more to me then the money.
I think you will have less of a fight getting a new cruise; because the cruise lines are having trouble filling the ships right now. Getting you on a cruise benefits them more then refunding your money. You will spend more money on the cruise: drinks, shore excursions etc. Plus if you enjoy the cruise you could become a repeat customer and the is what all businesses want.
This is my personal opinion. I have not been in this situation so I can't tell you for sure what is the proper way to go. That is up to you to decide. I'm not a lawyer and I don't know the laws or anything about contract law. I'm a finance major so my opinions are shaped by what I know of how business works. Good Luck I hope it works out of you.