"What is his direction?"

Translation: מה הכיוון שלו?

[MoriaGandi]

מה הוא הכיוון שלו
What is the difference between מהו ומה הוא?

[AlmogL]

They are the same: מהו = מה הוא, מהי = מה היא, מהם = מה הם, מהן = מה הן.

[Jacob29928]

When would you leave the "is" implied, versus expressly including it?

For example, isn't it also correct to just say, "מה הכיוון שלו" and not necessarily use "מהו" or "מה הוא" ?

Is it just a stylistic difference or is there a difference in actual meaning?