Is written translation easier than oral translation? How?

Neither. It all comes down to the translators themselves. Some of them prefer written than oral, and vice versa. Everything is a mere style in life. I hope my answer gave you a better frame of view.

Thanks.

I think so. In written translation, you have the time to think of the best word or phrase to render the exact meaning and review your work, while in oral translation you don't have the luxury of time to do so. If you give yourself time to think of the best translation (oral translation), you cannot keep up with the speaker, and so you will miss some part of what he/she says.