Some of the numbered red dyes are a migraine trigger for my wife. Naturally sourced dyes don't seem to trigger that reaction, although I'm sure that some people are sensitive to cabbage extract as well.

I'm a bigger fan of not adding colors to things that don't need it, but I still appreciate naturally sourced colors.

Red cabbage has been experimentally tested for far longer, and by far more people, than Red #40. I'm inclined to trust it more.

Well, potentially quite a lot of benefit:

https://www.cbsnews.com/news/food-dyes-linked-to-allergies-a...

The actual report seems rather weak. Some people have an allergic reaction to it, and some mouses may have tumors growing a bit faster - when over 5%(!) of their diet is red dye - and only in one of the three studies.

There are also people allergic to yellow food dyes (for example, tartrazine).

Of course, there could be a downside if there are more people that are allergic to the replacement. But the replacement is still a benefit to people allergic to the original ingredient.