So let me say right away that self-publishing is either
a)Vanity publishing or
b) publishing yourself via Amazon Kindle. (I've not investigated Smashwords, Nooks, Kobos and the like yet. My learning curve has reached astronomical heights in figuring out the Kindle process, and I'm resting on my laurels for a while.)
The independent e-publishers, on the other hand, are more willing to risk taking on an unknown author. They vet the offered work and reject or accept according to their varied criteria.Their editing levels are varied, too, and so are their royalty rates and contractual demands. But it must be remembered that the range is wide, and while one end offers low quality writing for sale, the opposite end offers high quality.