When presenting two values, I prefer to use the same scalar. I think this came from my Chemistry teacher, who is my idol. That had to do with how many decimals for calculations.
An article about the state budget made the point that cutting a sales tax on tampons would remove $9 million of a $26.9 billion budget. I would prefer to write it as $9 million and $26,900 million. (Maybe $0.009 billion and $26.9 billion.)
The idea is to present the numbers in such a way that the reader doesn’t have to do mental gymnastics. Though the difference between a million and a billion is not that intuitive. An NYT piece illustrates it as:
- a thousand seconds is 17 minutes
- a million seconds is 12 days
- a billion seconds is almost 32 years