The new guns give up HE alpha strike, fire chance, AA power and turret rotation speed for a 20% rate of fire increase, an additional rifle (or two) and an additional 1km range. While this ends up being a significant increase over the Hatsuharu's DPM, this is not enough for the new tier 7 destroyers to make up anything more than last place on the new charts. The Akatsuki comes close to the Leningrad in raw HE damage but not enough to challenge even that low DPM destroyer. So if either of these two ships are intended to be "gunships", then they're really falling short of the mark. While the new destroyers retain the "comfortable" gunnery of the Hatsuharu, including flat shell arcs and decent potential stealth-firing windows, they're not really to write home about. Enemy destroyers should respect the fire coming off these ships -- the Akatsuki in particular, but they are not decisive weapons.
So does this mean that the Akatsuki is the torpedo ship and the Shiratsuyu is the gunship? But wait, I'm totally forgetting the potential of the Hatsuharu's optional Torpedo Reload Booster which can be swapped for instead of her Smoke Generator. This would accelerate her reload to a mere 30s each time it was used. If we factor in a premium version (240s reset timer), we get the following values for the Hatsuharu over 10 minutes:
This really seems to solidify the Akatsuki as the torpedo ship and the Shiratsuyu as the gunship... until you realize that not only does the Shiratsuyu get Torpedo Reload Booster as well, she doesn't have to trade out her Smoke Generator for it. What's more, this darned thing accelerates the reload to 5s. Yes, five seconds. That's it. This means her 8 launchers can spit out sixteen torpedoes inside of 7s if you're fast on your trigger finger. So here's how the Shiratsuyu looks now over 10 minutes.
So while the Akatsuki maintains a superiority in the sheer volume of torpedoes she can launch, the Shiratsuyu offers a difference in game play styles, allowing you to effectively land monstrous alpha strikes on command with the use of her consumable or deny a vast swathe of ocean with a wall of torpedoes that outdoes even the three quintuple launchers on the Shimakaze. Keep in mind, these are the exact same torpedo between these two destroyers otherwise. This is the same 10km range, 62 knot top speed and 17,233 alpha damage. Enjoy.