The difference between 5x HVD which I used for the winning run and 5x Railgun is only 145 kinetic dps though. But a big issue with HVD is rate of fire.
It's a mix of high DPS, lower flux use and much better tracking.
Did try all arbalest, all railgun, and all HVD setups against the same fleet and HVD has a very consistent problem with being overwhelmed where the other 2 just smashes the enemy.
Executor needs all the flux dissipation and capacity it can get to keep it behaving as it should be. If it gets in a bad spot with flux it starts to use its weapons very poorly and spirals out of control from there.
Funnily enough you could sub Pulse Laser for railgun in the hybrids I think if you can handle the flux, they have the same range due to EBC if you don't have BRF and almost same anti shield dps.
Tried 2 pulse lasers in front hoping it'd help with clearing frigates, got completely smashed with flux used on something that's not kinetic.
Also tried autpulse+ion pulsers, best not to talk about that
Autopulse with some heavy mauler support works very well, the AI just can't pace itself and always gets caught with high soft flux buildup.
From there it's the usual song and dance, firing weapons all over the place, wiggling around, slow inevitable destruction.
For HVD vs Railgun, it should be pretty straightforward to put some Railguns on the medium ballistics and HVDs on the medium hybrids, and then do a side-by-side comparison of their total damage via the Detailed Combat Results mod.
Right, I forgot to mention, this is assuming Aggressive officers which will naturally try to head in to the range of the shortest-range weapon. I pretty much always use Aggressive officers so that's more or less an assumption for me.
Going from aggressive to steady to cautious on executors reduced suicide rates to something like 10% of the original.
Battle goes from hopeless and frustrating to being about avoiding that 1 casualty.
Most of the time cautious does a good job of actually staying at range and focusing fire instead of blocking.
Doesn't matter what officer type you are using, you can only compare weapons by actually running the battles with each loadout.
(also, hybrids are wide arc turrets so whatever you put there will obviously look much better)