Lately playing co-ops using Chapy and then Dmitry ships I citadel easyly 2 or three bots Smolensk. JB I don't remember any special moment. From Thunder I have bad memories when playing DD, they hurt me badly. About spending coal , in spite I find fragile its broadside, I would go with Smolensk for being a polemic ship, and people saids is good for solving directives and playing in co-ops. I think the enemy's bots don't care the HE spam.
The JB you can buy with cash, or will be available in Santa boxes. Being a tier IX, assuming the gambling will be the same you have a chance to get it . Smolensk it seems will quit for good, while JB you could have similar ones in the French in tech line. If I were you, this is what I would do:
1)Buy JB with doobloons real money, or wait Christmas and try gambling.
2) Buy Smolensk with coal.
3)Then obtain Thunder by collecting more coal next.