The Bismarck 1943 is the only one of those three that has more than a marginal difference from the main ship. Despite what SkaterBeast said, it's not so much slow as only having average speed, which is fine for sparring with BB3s (including 2nd Tier EBB3) and lower, but its lack of durability AND speed makes it a bit of a chore to go after BB4+. Though when it does, it hits like a sledgehammer, as the 14.96" trips nearly blockshot and hit almost as hard as KM 16". You can easily cripple most BBs with just one good salvo.
The O-Project II 1942 is literally an O-Project II with a slight speed buff and an extra support slot. That's it. The 8 supports, however, make it VERY good for leveling mid-level crew, and it therefore makes a very useful workhorse for grinding supports and sailors from other lines/nations. And frankly, the O-Project II, as is, is one of the best regular BB3s, with the EBB version fairing quite well compared to most EBB3s - it's fast (I've run 45 with full crew), has good reload and range, and despite having the weakest broadside, it still hits hard to do the tight spread. However, the attempts to give an alternative to the 14.96" trips have been less than stellar - it can fit H39 Ns, but the damage reduction of dropping to 6 guns with lower accuracy and almost no range increase just makes it not worthwhile.
The H41 is even closer to its non-event counterpart. It's just an H39 with an extra support slot and a few modest changes (some actually being nerfs). Same guns, same strengths and weaknesses. This, it's about as much better than the O-2 1942 as the H39 is than the O-2. While nothing special, it's still useful in how it helps you level up an extra crew member.
