I dont get it... the Kortul is pretty much equal to the Kol. It has nano jammer (vs strikecraft) the power diverter thingy (shield and weapon buff) and... what was it... anyways it doesnt have an ability that even comes close to finest hour. Yeah you mentioned that the Kol has to level up to get there, but even before then it has pretty much equal abilities to the Kortul.
You are forgetting disruptive strike, the second best capitalship killer ability after disrupt antimatter, and its passive. But I'll break it down for you by capitalship battle.
Level 1 Kol versus level 1 Kortul. Kol can pick Gauss rail gun for extra damage or Adaptive force field for endurance. The Kortul will pick Power surge, which by itself protects to Kortul better than Adaptive forcefield, plus give the Kortul a damage boost. Kortul wins.
Level 2-5 Kol versus same level Kortul. Kortul gets disruptive strikes, which is passive, depletes the Kols antimatter and make it longer for it to use its abilities. The Kortul will be able to use the much better power surge for the whole battle while the Kol, which always has antimatter issues until it gets finest hour anyways, will quickly run out of antimatter. Kortul probably won't even have much damage at the end as power surge will have healed it all one on one.
level 6+ kol versus level 6+ Kortul. You are right that finest hour is a better ultimate ability, but at this point the Kortul will have tier 3 power surge and disruptive strikes. Kol will be able to get more Gauss rail guns off but disruptive strikes will negate most of the extra antimatter finest hour gives, while perhaps doubling the cooldown time of finest hour. Meanwhile the Kortul is healing 55 shields per second most of this match, which is far more than the Kols normal weapons can do to it. Once the Kol runs out of antimatter to fuel GRG, it has no chance of overcoming power surge.
Granted, you will almost never have a 1 on 1 capitalship battle without supporting ships. But since neither of these ships have abilities that help its fleet, it doesn't matter, if the two fleets are equal the Kortul will beat the Kol every time.
But hey, don't take my word for it. Test it yourself. Or go online, and find out that pretty much any cap is more useful than a Kol. Getting a Kortul as a second or third capitalship can be a good move. Building a Kol outside of facing insane amounts of strikecraft is just suicide in a competitive match.