Picking between the two can be difficult, alot of players have gone for the IM because it can be alot easier to use, good range and firepower aswell as such a small frame makes it turn out quite overpowered in experienced hands, being able to use AA is unlikely.
The Kronstadt can also be a very good ship, slightly higher range but lower damage and easier to hit, it can be unkind if you make mistake, but it follows a design much closer to the BBs that follow it so you might learn a bit more from it, is perfectly viable, just a more defensive play style. AA gunners recommended. As previously mentioned it benefits more from good support and its one of the more nimble SN BBS.
Also, some players find the lines on the IM irritating to use since, in order to point its guns the way it does, it lays them out FRONT BACK FRONT BACK, instead of FRONT FRONT BACK BACK, causing lines like;
\ / \ /
\ \ / /