It depends. Princess is good if you want to be able to cancel for "any reason". Most other insurances have specific reasons in order to get your money back. But, if you buy a cruiselines insurance, if the cruiseline went out of business, you would not be covered. What you need to do is check out all different sorts of insurance and decide. But decide quickly, because many insurance policies do not cover pre-existing conditions if you do not get your insurance within 2 weeks booking.
We also us CSA - I am very impressed with their service. My brother and his wife had to cancel a cruise because of a death in the family. They were great to deal with and covered them completely.
Also, if you buy two separate polices rather than one to cover a couple it not only saves you money but also gives you some additional luggage insurance etc. You will need to call them to do this as it doesn't show this option on line. You may even have to tell the agent that you want it done in two polices as they aren't all familiar with how this works.