We did this trip awhile ago and I looked into all my options. What we did was book through NCL and paid the $80 per person. Do NOT BOOK the express with NCL! When you get to the park you can upgrade your ticket there at the Universal price, it will save you tons and it won't take you much time at all. You can do it right at the entrance, there are so many ticket booths available and you won't have to wait more than a minute or two. You definately need to upgrade though, this time of year is crowded at the parks and you will appreciate paying the extra $20 or so per person to not have to wait in long lines. So, you can do it through NCL for about $400 and you won't have to worry about renting a car, parking it, returning it and all that. The NCL bus will be waiting for you when you get off the boat in the morning and will drop you off right at the entrance to the park. If you rent a car you'll have to pay to park and you'll probably end up quite a ways from the entrance, not to mention the hassle of actually renting the car. Also, if you take the NCL bus you'll have plenty of time in the park. I know that's a concern for many people but with the express pass you'll be able to ride anything and everything you want and still have time left over.
Oh, the only drawback to this is that you are taking the very slim chance that the park will sell out of express passes. They only sell so many per day. But, I wouldn't worry about it unless you were there on 4th of July week or during Christmas break. You'll be there early enough in the day and from what I understand, they usually have express passes on busy days until about noon or so. You could go to a Universal message board to get confirmation of that, if you're concerned. I'll tell you this though, when we went it was a very busy time and we got there about an hour after the park opened. There was no problem getting an upgrade from the park, they still had plenty left. Hope this helps.