There are key differences in the pre-booking experiences on Holland America vs. Princess vs. Royal Caribbean cruise lines that I think are important for your to know
Booking flights thru the cruise lines
Royal Caribbean doesn't let you see the flight options till you book unless you call into the cruise line. The reps are very helpful but it's annoying you can see your options till you book.
Princess and Holland allow you to look at the ez air flights prior to booking so you will get an idea of options and prices without have to go to the airline or flight hub sites.
Holland also has a nice feature allowing you to fly out of a different city other than your disembarkation city in Europe and at any date/time after your cruise. I am currently taking advantage of it.
All cruise lines have same day arrival protection and they always offer the earliest direct flight to you if it's available. These flights get there in sufficient time to make it to the cruise for embarkation.
All cruise lines will offer you the flight in CDN dollars but because they are a US travel agency, you will have to pay for your seats/ bag on Air Canada in USD. Annoying. Fortunately it's only Air Canada as I have flown on European carriers and they will price in CDN.
Shore Excursions, Internet, transfers and other pre cruise purchases.
The biggest difference between RCCL and Princess and Holland are the pre-sales they have on shore excursions. The prices stay the same pre and after on board on Princess and Holland America.
RCCL and Princess let you use your OBCs to pay for pre-cruise purchases. Holland America does not (and this is very annoying as sometimes shore excursions sell out).
All have sales on the internet packages pre-boarding.
I have begun to find that the cruise lines are charging much more than a taxi or uber or shuttle to the cruise port in Florida. I also find they use less and less buses and your wait for a cruise line bus can be up to an hour. I stand in the taxi line and often am asked if I am willing to share (which I do as one person for savings).
Cruise line apps and pre communications
All three cruise lines ask you to download their app. Princess and RCCL are comparable and pretty easy to use. Holland America (even their tutorial) is awful. You can't even see you cabin number and basic info.
All are needed if you are going to get the internet package.
All allow you an online boarding pass in the app.
Pre cruise emails from the Cruise companies
You will receive almost nothing from Holland, but Princess and RCCL will communicate a bit.
Non of them advise you on the new visas required for UK or Europe. One of the reasons you should book thru a travel agent. I am currently in the process of getting the ETA for UK ($10 pounds) and the EITA is not ready yet for Europe.
Booking a Guaranteed Cabin
All don't let you know til about a week ahead of the cruise departure. Once on Holland it was the night before departure.
I book a guaranteed ocean view or balcony on Princess or Holland and have mostly had good cabins (but I hated the solo ocean view on Koningsdam. If you don't want the solo ocean view on Holland you have to pick the "f" Oceanview guaranteed cabin option vs the OO. I still don't have the assignment yet on Holland and hope this works to get a normal ocean view cabin.
I have had horrible cabins on RCCL guaranteed so I recommend picking your cabin. They are known to give out the worst cabins to those booking the guaranteed option and never upgrade you.
Both princess and Holland have given me in-category upgrades on cabins (i.e a better ocean view) or an upgrade to a balcony (much rarer).
Hope these comparisons help
Marcia