Both sentences are grammatically correct, both convey exactly the same meaning, and do it without ambiguity. Both get across what I suspect will be a remarkable fact to the reader.
As someone who spent his career in accountancy, and this is entirely a matter of personal presentation, my own way of saying it would be:
'Expressed as a percentage of revenue, Corporation X spends more on insurance, than Corporation Y on employee salaries.'
In accountancy one thing with which you constantly battle is the avoidance of misunderstanding. Absolute clarity as to what you are saying is paramount. And here, I am supposing, that these may be two very different companies and possibly of vastly different sizes. And I also assume the purpose is to emphasise to all concerned the huge amount that X is spending on insurance. So you have to make it absolutely clear from the start that you are talking of 'percentage of revenue'and not absolute amounts of expenditure. So that is why I put it, clearly stated,at the start of the sentence.
But I repeat, there is nothing incorrect about either of your sentences.