Bahaullah says that each of the Manifestations had a specific Mission, and a Revelation that was suitable for their own time.
So, the Revelation of Muhammad is not suitable for our Age, and the Revelation of Bahaullah is not suitable for the Time of Muhammad, I quote Bahaullah:
"...each Manifestation of God hath a distinct individuality, a definitely prescribed mission, a
predestined Revelation, and specially designated limitations. "
Also, He says, Their missions or revelations is like a physician who comes with specific Remedy to cure the problems, so, just as each Age has its own Problems, so, also the different is the remedy:
"The All-Knowing Physician hath His finger on the pulse of mankind. He perceiveth the disease, and prescribeth, in His unerring wisdom, the remedy. Every age hath its own problem, and every soul its particular aspiration. The remedy the world needeth in its present-day afflictions can never be the same as that which a subsequent age may require. Be anxiously concerned with the needs of the age ye live in, and centre your deliberations on its exigencies and requirements.” Bahaullah
Bahá'í Reference Library - The Tabernacle of Unity, Pages 15-55
Now, suppose, last time, a person had flue. The doctor gives him, remedy for the flue. Another time he has a broken leg. He would have a different remedy and solution.
It is not that the remedy of flue is better than remedy for a broken leg, but each one is meant to cure the specific conditions. Likewise, the revelation of Bahaullah, Muhammad, or Buddha, are not better than each other. It is just that each is suitable for the Problems of Their Own Age.