Slashing Grace by definition turns katana into one handed piercing weapon and able use it with class features and such plus add Dex bonus than Str bonus to dmg with it. But it does not turn weapon finessable (ironic enough considering it asks weapon finesse feat). However ideal weapon for katana feeling would be dueling sword (finessable with Exotic Weapon Proficiency, 1d8 weapon and lots feat and archetype support).