If you're not sure that arriving a day early would do it, I would arrive 2 days early ,otherwise half of your trip will be gone, because a lot of these stops have no airports or one flight a week.
On Hal there is not much to write home about too, no entertainment and mediocre food, so how bad can it be on the new Maasdam? I would look at more at the itineraries.
With the mariners discount of 50 % I always thought that the prices were reasonable, but since Carnival is now a zombie company I guess they need the money.