Between the two BB3s the O Pro2 is normally considered the better GB farmer. However, with longer range, slightly lower salvo damage and the gun placement, the Bismarck more closely resembles future KM play style.
If you compare just the BB3s, you have the O Pro 2 with slightly less range from its trips, a more durable ship and 7 support slots (so you can level 12 of your 14 BB crew sailors at once). But the Bismarck, while softer and with only 6 supports, also has slightly more range. In most other respects they are the same. The OPro2 is able to use the Bismarcks duals if you want, but while you gain range you lose a lot of damage. Of the two, the Opro with its triples hits harder.
For the BB1/2s of the lines, the Bismarck line offers the better ones in my opinion. None of the ships on either line are especially well suited to AA, they're all just as capable at it as each other really, though not overly effective with only 3 evenly spaced gun each side.
