"Which one is the best" is obviously a question format, so it makes sense that " which one the best is " should be the correct form. This is very good instinct, and you could even argue that the grammar is good, but at best it's unnatural.
"Which one is the best" is obviously a question format, so it makes sense that " which one the best is " should be the correct form. This is very good instinct, and you could even argue that the grammar is good, but at best it's unnatural.