I wouldn't get caught up in the term "inside Alaska". Juneau, Ketchikan, and Skagway, are pretty much the meat of an Alaska cruise. Glacier Park is the most popular, but if you visit Hubbard glacier you probably won't even know the difference.
For most people, Alaska cruises are more about the destination and not the ship. Based on your description above, any of the cruise lines will provide good entertainment, service and food. However; based on your age the NCL Pearl may have more activities that interest you during the non-port time.
I understand you have a tight budget. It is rather low for an Alaska cruise. Especially if that is including airfare. Balcony cabins are highly recommended for an Alaska cruise and they cost much more because of the demand. You may have to go with an inside or outside which is better than not going at all. You also need to consider what you may spend on shore excursions, on board expenses of gratuities, drinks, casino, spa, and gifts.
When comparing cruise prices it is very important you are comparing apples to apples. This is why using a good cruise agent is important. They can help you pick the right ship, the right cabin and location, and the right itinerary. They can also point out pros and cons. Websites like VTG can be appealing with the word "cheap", but "cheap" can be deceiving.