No different from: (chẳng) khác gì, khác nào

Khác gì asks "how is it different from …?" without wanting an answer: it says two things are the same. Không khác gì and chẳng khác gì (no different from) mean exactly the same: Phòng này nóng chẳng khác gì cái lò. This room is like an oven.

Put what you're describing first, then (không) khác gì, then what it's as good as. That can be a thing, a person or a whole action: Kẹt xe vầy thì khác gì đi bộ. With traffic like this, we might as well walk (in Hà Nội, Tắc đường thế này).

It's usually an exaggeration, so it carries feeling. It can be praise: Anh nói tiếng Việt không khác gì người Sài Gòn! You speak Vietnamese just like a Saigon local! With an action, it says what something amounts to, often as a complaint: Nói vậy khác gì chê em dở. Saying that is as good as calling me useless.

Như (like) and bằng (as … as) compare one quality: cao bằng ba, as tall as Dad. Khác gì says one thing might as well be the other. Khác nào and chẳng khác nào mean the same and are more common in writing.

With nhau (each other), it's usually a real question: Hai cái này khác gì nhau? asks what the difference is.