Hadiths were written by people who never lived in Arabia and they were in fact from places so far that it is not worth debating. Also, Hadiths were written 200 years after Prophet's death. Not one contemporary. All based on Chinese whispers. No one ever saw actually Prophet saying all the things that are mentioned in Sahih Hadiths.
Gospels were written by people who lived during the time of Jesus and saw Jesus perform all the miracles.
Seems like your problem is with oral tradition/transmission. Also, it is false that hadith was not written until 200 years. At 200 years scholars just complied it and developed usool. Written hadith is found right from the start especially with development of Seerah. Seerah was developed and compiled even before hadith by earliest generations. Fiqh even has hadith as a fundamental source of knowledge after Quran. Also, we know that oral transmission of hadith was a phenomenon to learn deen in the time even first generation.
By the way, are you not a Muslim? Not that it matters in this argument but it just lets us understand better that where are u coming from?