Datura is an annual - brugs are perennial. The flowers on a brug hang down - the flowers on a datura point upward. Both plants can be equally fragrant but any frangrance is strongest in the evening or at night.

Not all species of Datura are annuals. Some Brugs smell bad. I had a plain white one that stunk like a lemon-scented cleaning product.

Daturas make spiky seed balls. Brug seed pods look a lot like okra.

What is common would vary by region. The ones I see being grown ornamentally most often are inoxia, wrightii, stramonium, and metel, of which only stramonium is reported to be a true annual. For those who are where the other three species would be hardy, planting seeds or plants in the ground would require more long-term consideration.

Agree, scent is subjective. To be more specific, I found the white-flowered Datura to be a chemical scent, not a typically floral one, a bad lemony, not good like real lemons. Similar to Magnolia grandiflora, but even less appealing. Other noses could absolutely interpret the scent of the same blooms differently.

The scent of these B. suavaolens blooms is very appealing, a more "regular" floral scent.

And I wanted to indicate that investigating to genus level is just a start regarding comparing the differences between the various species in the two genera. It's not a "you've seen one Brug, you've seen 'em all" kind of thing. But it is a good start.

I don't want to argue with you but there are very few locations in the continental US where daturas would be considered fully perennial. So 99% of the time they are sold and grown as annuals.

And I know you are just being helpful but asking questions about the differences between the two genera would hardly indicate a desire for the sort of specific and technical knowledge a serious investgation would turn up :-)