The point of this blogpost is to consider briefly some important differences in structure and form between the Old Testament and New Testament. I hasten to say that none of this is to rank the two; the differences do not make one better or worse than the other.
The focus of the New Testament is really over over a very short time period, about thirty years; the Old Testament stretches for at least over 15oo years. To elaborate: Even if we exclude the pre-Abraham parts of Genesis (Creation through the Tower of Babel), it begins around 2000 B.C. and lasts until after 500 B.C. The New Testament, on the other hand, if we exclude Revelation and the relatively short discussion in Matthew and Luke of the births of Jesus and John the Baptist, goes only from Jesus’ ministry (beginning around A.D. 30) through Paul’s imprisonment in Rome (maybe thirty years later).
So you have the NT authors all writing about what happened before them all, while the OT authors are spread out over a long period of lifetimes. This makes “undesigned coincidences” much more possible in the former than the latter. Also to that point is the fact that the OT authors are writing about a much wider range of topics than the NT authors, who are all focused in one way or the other about the events and teachings of that itinerant Jew.
Even the genres are different. There are nothing like the OT’s five wisdom books in the New Testament. The NT epistles and the various OT prophet books (major and minor) have in common that they are generally non-narrative and instructional, but their tones and format are quite different. Likewise, while there are OT biographical accounts, the NT Gospels are distinct. Acts is more similar to OT historical narratives, and Revelation a longer version of some of OT prophecies (like Daniel and Ezekiel).
The unity of the Old Testament comes from a predominant focus on one people and its relationship with God, while the New Testament is ultimately focused on all mankind’s relationship with Jesus Christ. I should note finally that the OT is about 3.3 times longer than the NT.
I think it would feel very different to spend a career examining the New Testament rather than the Old Testament.