Is there any downside to picking your cabin category but not your specific cabin, and seeing if you get upgraded? I can understand why you'd want a guarantee if you have a specific area of the boat you'd like to be in. But I don't think we'll care. Also, how often do you passengers get upgraded?
You have a slightly better chance of an upgrade by booking a guarantee catagory over a specific cabin. It all depends on how full the ship is and what catagories sell out first. Best of luck to you.
The negative side about booking a guarantee is that the "upgrade" you receive may not be that great of an upgrade. Some folks will jump up and down because they received a three category upgrade, when in fact the cabin is three doors down the hall, and it is the identical layout as the category they had booked. HAL cat N to cat K. Or it could be a one category upgrade and be exactly one deck above and right under the pool. Carnival Cat 8B to Cat 8C.
Don't get me wrong, there are many times when jumping up and down is warranted but many times it is just another cabin on another deck or just down the hall.
You will hear from the folks who receive the "Miracle Upgrade". Those are upgrades from lowest category balcony to a Suite (If I received one I would say something) but they are few and far between. The majority of upgrades are within the same level of cabin. Inside to Inside: Outside to Outside and Balcony to Balcony. Hundreds of upgrades are done every day by the cruise lines and the vast majority aren't too exciting.
If you want that, fantastic, aft/stern balcony, with wraparound deck, then you better book it, because there is little chance you are going to be upgraded to it. Nor is there little chance you are going to get a suite close to the elevator.
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