Which Ferry?

When you're looking at crossing Cook Strait (between the North and South Island) I highly recommend traveling by ferry, but which one? There are two main shipping companies for crossing the strait. The Interislander is the longest running passenger service however in recent years Bluebridge has begun catering for passengers, and they both have their pros and cons.

The Interislander has 3 vessels and having been around for longer has a much larger variety of onboard entertainment from movies to gift shops, kids playgrounds, work stations and a club class lounge, however it costs to see the movie which is usually a second rate movie and the cinema isn't the most comfortable, and the gift and food shops are priced to target tourists. The ticket prices range from about NZ$35 - $60 per person depending on ticket availability. I wouldn't pay $60 unless I had no other option. It is a 3 hour trip.
http://www.interislander.co.nz/mainpage.asp

The bluebridge on the other hand developed from a freight shipping company and had a ship refurbished in 2003 to take passengers. The good thing about bluebridge is that there is one set price $45 per person (adult). There is no movie cinema but they do play a couple of family movies on large screens around the ship but they can sometimes be hard to see or hear. There is a cafe and a snack shop onboard which is also quite expensive. I have found that in rougher weather the Bluebridge doesn't seem to roll around as much but the trip does take 20mins longer
http://www.bluebridge.co.nz/passenger.htm

All in all it's only 3 hours and if it's nice weather you'll probably spend most of the trip on the deck, when I travel I usually take whichever ferry I can get the cheaper ticket with, but check out the websites and I'll let you choose for yourself.