Differences in the basic premise, perhaps. Which is poly vs monotheistic
Born of a virgin (which was a mistranslation from the OT anyways hehe), return to life after 3 days, adored by 3 kings upon birth, crucified, star in the east, teacher at 12, ministry at 30, walking on water etc etc etc. Pretty much his entire life.
As far as sumeria and judaism, you have the flood, garden of eden etc
There are many possibilities to judaism being a coincidence, or the same religion and abraham finally got it right, than with christianity.