Adjusted for advances in technology, I think the Excelsior and Ambassador were probably intended to be more tactically oriented than the Galaxy, which was more outfitted for exploration. So a modern retrofit of the aforementioned ships outgunning a Galaxy actually makes sense. Pay attention to your TNG episodes, and you'll see that the Galaxy was quite pathetic in combat. So if anything, Cryptic is following canon.
The Galaxy-R, and like wise the Galaxy-X have a Turn rate of 6, 39K hull, and 1000 crew.
The Excelsior refit has a turn rate of 8, 39K hull, and 750 Crew.
The Ambassador has a Turn rate of 7, 39.5K hull, and 700 crew.
The Assault Cruiser refit has a Turn Rate of 7, 39K hull, and 800 Crew.
The only real difference between the Ambassador and the Excelsior is the flip flopped Tac / Sci BOFF stations. The Galaxy R/X has a Lt Comm Eng Station, and the Assault Cruiser Refit has a universal Lt Station.
One other really odd part about this, is that the Ambassador and the Excelsior are RA level ships, the others are VA rank. If you compare them with the Oddy Command Cruiser a VA level cruiser, it's rather sad.
Outside of that i's really just differences in special consoles they have, but most of them can be swapped around.
this is by far the bulkiest cruiser apart from a odyssey out there T5 wise it also gives sci captains a cruiser in which they can use actual powerful sci powers in on top of that it is on par with everything but the excel in turning cruiserwise so i feel like this ship has potential and i would love to fly that ship around and get to know how it will perform in battle.