Here's a source that cites Both Dates as legitimate:
Historical background 70 CE-1917 - Israel & Judaism Studies
"Jews have lived in the Land of Israel for nearly 4000 years, going back to the period of the Biblical patriarchs (c.1900 BCE). The story of Jewish life in ancient Israel is recorded in detail in the Hebrew Bible (the Christian "Old Testament").
The dispersion of the Jewish people is traditionally dated from the destruction of the Temple in Jerusalem in 70 CE, an event considered by the Romans to be a victory of such significance that they commemorated it by erecting the triumphal Arch of Titus, which still dominates the Roman Forum. The Roman historian Cassius Dio records that in a subsequent revolt in 135 CE some 580,000 Jewish soldiers were killed; and following that revolt the Emperor Hadrian decreed that the name "Judea" should be replaced by "Syria Palestina" - Philistine Syria or "Palestine"."
The key, for me, in preferring the 70AD date is that all the genealogical records were burned and forever lost in that event, rendering any "reconstitution" or "Reformation" of the Jewish Theocratic Nation of Israel, per the terms and requirements of the Sinai Covenant that inaugurated the Biblical nation of Israel in the first place, impossible forever.
Today's Israel, in contrast, is a Multiethnic Conglomoration of peoples who have entered into a Democratic contract with one another to form a modern Secular Nation founded on the principles that arose out of the European enlightenment of the 17th and 18th Centuries. It has no relationship whatsoever (outside of geography and moniker) to the pre desolation Hebrew Theocracy that once shared its name and general location.
It is no more the "reconstitution" of Biblical Israel than modern Mexico is the "reconstitution" of the ancient Aztec Empire.