These are very late game tests, if you combine kinectic artillery with lvl3 plasma and max shields/armor. Most of the important fights are fought with less that optimal weapons, so need to choose either kinetic or energy weapons. BB probably is in better spot between 2250-2350 when cruisers aren't in optimal shape.
Big part of the problem seems to be shields. Cruisers get 3x M, which gives 630 shields and 33.6 regen. BBs get 2xL which is 840 and 30.4 regen. 2x Cruiser has huge advantage here vs 1 BB. In my initial tests full kinetic BBs had very hard time getting the shields down from cruisers after they initially shot many of them in bad shape.
I presume many of you forgot admirals and fleet academy in testing. At least I did from my first tests where BBs always got beaten badly

All fire rate, range, tracking and chance to hit bonuses help BB fleet more than BCs as BBs do more damage in early battle. If they do enough here, they win.
I add both fleets academy bonus (5% fire rate, +3 chance to hit, +3 tracking). Also BB fleet to 5* aggressive leader (+8 and +25% % fire rate) so BBs got total of +38% fire rate, +17 tracking and +8 chance to hit. BC fleet got 5* leader with 10% hull points. Fleet sizes are 80 BC (2x kinetic artillery + 2x M gauss) vs 40 BB (giga cannon + 4x kinetic artillery).
I tried this battle quite a few times and BBs kept almost always. It just depends if BBs randomly concentrate enough damage to same ships to kill enough of them before meeting. Here are last 5 tests where I kept these same settings.
1. BBs won. Losses 80/80BC and 30/40 BB.
2. BBs won. Losses 80/80BC and 23/40 BB.
3. BBs won. Losses 80/80BC and 31/40 BB.
4. BBs won. Losses 80/80BC and 28/40 BB.
5. BBs won. Losses 80/80BC and 34/40 BB.
Giga cannon is very good until the fleets meet, but doesn't work well after. Before fleets met, giga cannon that took 33.3% of slots did 41.4% of hull damage and 36.9% shield damage, so it's often worth using.