In this case, there is no advantage to being married.
It's only relevant if one spouse earns more than €33,800 and the other earns less than €33,800.
If both earn more than that (as in the OP's case), there's no advantage. Easiest to think of it like this:
1. Boyfriend and girlfriend both earning €33,800 pay the same amount of tax as a husband and wife earning €33,800 each.
2. Boyfriend and girlfriend earning €42,800 and €24,800 pay more tax than a husband and wife earning the same. Reason being, they can share the extra €9,000 of the wife's otherwise unused standard rate cut off point.
3. Boyfriend and girlfriend earning €42,800 and nothing pay more tax than a husband and wife earning the same. Reason being, the €9,000 of standard rate cut off point referred to above and the extra €1,650 tax credit the husband can claim for his wife.
But once you both earn reasonable money, it's all moot.