For our honeymoon we have booked the Adventure of the Seas aft cabin (D1) 1690, however now for the same price we can upgrade to a Deluxe Stateroom Guarantee.
You are currently in a superior balcony stateroom. From the Royal Caribbean website is the following description of the stateroom you are in ...
Two twin beds (can convert into queen-size), private balcony, sitting area and a private bathroom. Rates vary from deck to deck. (188 sq. ft., balcony 50 sq. ft.)
You want to "upgrade" to a deluxe balcony stateroom guarantee (again from the Royal Caribbean website for the stateroom you want to "upgrade" to) ...
Two twin beds (can convert into queen-size), private balcony, sitting area, and a private bathroom. Rates vary from deck to deck. (173 sq. ft., balcony 47 sq. ft.)
I am not sure why you believe that moving from to a stateroom that is 15 sq. ft. smaller with a balcony that is 3 sq. ft. smaller is an upgrade.
Since it is a guarantee cabin we will not be able to choose the location of the cabin, however there is a chance we could end up with a really nice suite. You have the best balcony stateroom in a prime location and you are looking to downgrade in the false hope that you might be upgraded. Sure, you might be upgraded to a junior suite, but don't count on it. What is far more likely is that you will NOT be upgraded, and if you are, the most likely upgrade is to a superior balcony stateroom, just like what you have now, except it will not be in such a great location.
Has anyone has experiences with this before. Also, I have never stayed in a Junior Suite so I don't know if it's worth giving up an Aft cabin. What is everyone's opinion should I stay in the D1 aft or change to the guarantee cabin? The problem with this is that you are expecting to be upgraded, and not just a simple upgrade, but an upgrade to a suite no less. This is the least likely of all the possible outcomes. Most likely you will end up in another balcony stateroom which is in a less desirable location, and you will spend the entire cruise brooding over your decision to give up a prime cabin location for a downgraded cabin in the hope of getting a two level upgrade to suite.
The only things a junior suite offers over a balcony cabin is priority boarding (which has a limited value - perhaps 10 minutes), a better bathroom and a larger cabin. If there are only two of you, I don't think the larger cabin has that much value.