“Which is better” and “Which one is better” mean the same thing when used as relative phrases. Both are useful, but “Which one is better?” is more common as a complete question. On the other hand, “Which is better” is often seen in sentences.
These phrases help you compare two or more things. For example, you might ask, “Which one is better, tea or coffee?” This is a direct question. If you’re writing, you might say, “He asked which is better, tea or coffee.”
Using these phrases correctly can make your communication clearer. They both serve to help you find out which option is the best among the choices you have.
So, whether you choose “Which is better” or “Which one is better,” you’re still asking the same question. It’s all about how you want to frame it in your sentence.