Please be aware that all of the statistics and performance discussed in this post reflect the version of the ship as she appeared during the testing period.
These are subject to change before release.
There's two big points to mention in regards to the Missouri's options. The first, during testing we had two camouflage patterns to play with. These both did the same thing, providing a bonus 100% to experience gains as opposed to the 50% normally provided by premium ship camouflage between tiers 6 and 8. This is on par with premium camouflage purchased for tech tree ships at tiers 9+, though, so it's good to see the Missouri keeping pace.
Premium Camouflage: There are two versions of the Missouri's camouflage. Both provide a 3% concealment bonus, a 4% increase to enemy gunnery dispersion and a 100% bonus to experience gains.
I spent a lot of time in Co-Op with the Missouri trying to isolate her credit earning potential. I suppose I owe the few not-bot team mates a sincere apology for my lack of performance in said matches. The only way to reliably get a measure of just how much the Missouri earned compared to other premiums involved getting myself killed without doing anything of consequence. A half dozen matches in the Missouri and the same done in the Tirpitz, Atago and Mikhail Kutuzov helped pin down the value of the Missouri's credit income.
I would absolutely recommend her for grinding. She is, hands down, the best USN training ship and credit earning ship in the game -- a fact that is unlikely to be challenged anytime soon. The only ship that comes close to her totals is the German Prinz Eugen for Captain Training, but the German ship doesn't come close to her credit earning potential. So if you want to earn bank and accelerate training up your Captains, the Missouri is a must have.
Is the Iowa-class competitive? You'd be a fool to take her instead of the Friedrich der Große, IMO. But this whole question is sort of moot with there being a distinctive lack of tier 9 competitive game play. If it ever comes up? No, don't use your Missouri. Use the Friedrich instead.
If you are selecting an AA build, you want the following choices to best optimize your firepower. This will provide extra range and extra DPS off of your AA guns. In addition, this build also adds to your agility, reducing your rudder shift time.
Recommended ConsumablesWhen it comes to premium consumables, it's easy just to splurge with the Missouri because of how many credits she tends to earn. The only players that need really concern themselves with their inherent costs would be those without a premium account looking to focus primarily on Co-Op. However, there are some that are just worth taking from a game play perspective.
Recommended Captain SkillsAgain, depending on whether or not you want to specialize as an anti-aircraft vessel or not will affect your Captain Skill choices. Optimally, you'll want to build towards specializing her for concealment and firepower, not for anti-aircraft duties.