A long time ago (before the 2015 Supreme Court ruling), I predicted that if same-sex marriage was ever legalized in the whole country, within five years the same-sex divorce rate would exceed the divorce rate among heterosexuals. Next year we should find out if I was right.
To compare the rates you need to control for length of marriage. You need to look at and compare only the short term marriages.
You don't want to compare the rates of those married for 3 or 4 years with all those people who have had 30 years to decide to end the marriage.