If you want to compare policies, try <http://www.insuremytrip.com>. There are several independent policies there which can be compared side-by-side for cost and coverage.
The only real advantage of Princess' insurance is the "cancel for any reason" coverage. If you think there's a chance a work-related issue or world situation might have you uncomfortable traveling, then opt for Princess. Remember, you don't get a refund, but a credit toward future cruise. 75% with the regular, 90% with the gold. Otherwise, the insurance offered independently is generally much better.