is Princess cruise in Europe any good?

There are some people, I don't know them really, but they want to travel to the Mediterranean Sea on a 12 day cruise and have excursions in Spain, Italy, France, Greece. They want to do this as a group cause they get discounts that way. If you've had experience, is Princess cruise in Europe any good? I heard Norwegian cruise line is pretty good to and also not expensive. Which is better for European travel, NCL or Princess? What are the pros and cons of traveling in a European cruise with Princess?