Which one do I use?

Each page puts our full write-ups of the forms next to each other, in the order worth reading them, with examples and audio. Nothing is abridged for the comparison.

• は vs がWhat the sentence is about, versus what performs the action2 forms
• に vs でWhere something is, versus where something happens4 forms
• たら vs ば vs と vs ならWhich kind of 'if' — and how inevitable the result is4 forms
• かもしれない vs だろう vs はずHow sure you are, from a genuine maybe to a firm expectation3 forms
• そうだ (looks like) vs そうだ (I hear)One form, two meanings, told apart by what it attaches to2 forms
• ようだ vs らしい vs そうだWhere the impression came from — your eyes, the room, or someone's mouth3 forms
• ために vs ようにWhether the outcome is something you control2 forms
• と vs やWhether the list is the whole list2 forms
• ごろ vs ぐらいA point in time, versus an amount of anything2 forms
• あまり vs ぜんぜんHow complete the negative is2 forms
• られる vs ことができるTwo ways to say 'can', differing in register3 forms
• あります vs いますWhether the thing that exists is alive1 form
• 前に vs 後で vs てからOrdering two events, and how tightly they are linked4 forms
• なければならない vs なくてもいいObligation, and its exact opposite2 forms
• ておく vs てある vs てしまうWhat the finished action left behind3 forms
• 尊敬語 vs 謙譲語Whose actions you are talking about2 forms