Note that what is written here is an opinion only. It is not meant to be a review of each weapon. Use what works best for you.
Swords. Still the coolest weapon. It is very visually pleasing to see the player character sheathe a sword then perform Iai Quickdraw. Being able to do this effectively requires a lot of practice though, making the cool moves a reward for the time invested in learning the weapon.
Spears. It still has the advantage of reach without sacrificing attack speed and mobility. Overall it remains to be a very solid weapon but is not too much fun to use.
Dual Swords. Back in Nioh 1 my go-to skill for this weapon was Whirlwind. It feels like it’s been nerfed in the sequel because it seems to have a smaller hitbox. It doesn’t hit as far as it used to. There are other skills, of course, but as mentioned Whirlwind was my favorite so it was discouraging to use this weapon.
Kusarigamas. My favorite skill, Blade Spin, has definitely been nerfed. It does not hit when the target is too close. This is more of an annoyance than a discouragement though, so the nerf was still manageable as opposed to Whirlwind.
Odachis. This weapon has a fair amount of complexity with the automatic stance switching as part of its moveset. Out of all of its skills Swirling Snow was the favorite. It’s simple, effective and brutal.
Axes. Slow and powerful. It will appeal to those who like doing one-hit kills.
Tonfas. One of the best weapons in the game. Several skills are multi-hit, making this weapon a top pick for imbuing elemental effects. For example, most enemies will get the Purity debuff from three tonfa mid-stance strong attack hits. If the tonfas don’t have the Purity element, the problem is easily solved by using Masaru as the guardian spirit.
Hatchets. The best weapon in the game. Advancing Storm allows players to steal turns from their opponents. To explain, games with stamina-based combat systems like Dark Souls, Nioh and Bloodborne give players a stamina cost per action. Once it runs out, no further actions can be taken until it is regained. That is done simply by taking no action, like not attacking, dodging or blocking. This makes the stamina regeneration period the opponent’s turn. Advancing Storm is a ranged attack, minimizing the need to dodge and sometimes even block. This means that stamina becomes dedicated to attacking, potentially allowing a player to never stop attacking and never lose their turn.
Switchglaives. This is for fans of Bloodborne’s trick weapons. Similar to odachis, switchglaives have a fair amount of complexity because of stance-switching. Unlike Swirling Snow with odachis though, there wasn’t a skill notable or fun enough to use.