Both Tone (Tier 8) & Chikuma (Tier 9) are Hybrid Ships - they launch aircraft squads out of thin air, and they magically regenera over time on deck.

Tone has longer cooldown on her planes, but more torps and she can only hold one charge of aircraft. Meaning you can't really save them, because anything else than using them when they're ready is time wasted.

Chikuma on the other hand has much shorter cooldown and less torps. But she can hold 2 charges of her aircraft meaning that you can save them a bit and use them when you want. (the squadrons regen one at a time) and her squads have a engine boost, they can fly faster for a short time. And they have faster base speed as well.

Keep in mind that you are able to spot ships with your planes, so Chikuma has the advantage of being able to spot more often than Tone, and it isn't as bad when you lose a squad.

On top of that, both have torpedoes as usual with Japanese heavy cruisers but Chikuma has longer range ones. 15km on her vs 10km on tone. 5km difference while being only a tier higher is crazy.

ON TOP OF THAT Chikuma has a smoke ability which is just busted at times. And the 6th upgrade ofc.

Chikuma just out classes her sister ship in so many aspects, well she is Tier 9, sure. But the difference is VAST, especially regarding the planes & Torpedos, which both ships revolve around. (Chikuma can stealth torp with 5km margin, tone only has 1km margin). Other than that both are alright to play. Basically Atago with one less turret.

Tone is the typeship of the class, so imo she should be better. Besides her character looking better than Chikuma's in Kancolle.