I was using dark mode in order to test it, throughout all the iOS 13 betas.
When the official build launched, I went back to light mode and couldn't be more happy!
In my eyes, dark mode looks more "techie" and light mode looks more clean and sophisticated, if we can say that about phone themes.
Apart from the looks of it, I believe reading black text on white, is much easier for my own eyes, which literally hurt whenever I was trying to read a pdf, or long texts in general.
It feels more natural to read digital text with the same look of a physical book or magazine.