First, Submit will accept any graphic novel in PDF format, but comiXology will only distribute the title after it meets their approval. Comixology isn't clear on what they are looking for, but they do say:
We reserve the right to reject any submission. We'll have a team of people looking at the quality of each submission. The high quality of our customer experience is the key to comiXology's success, and something that we do not take lightly. For this reason we will be choosy about what type of content we accept on our digital comics platform.
That almost reminds you of Apple's process for accepting content into iBooks, doesn't it? It surely does not resemble how any other ebookstore operates, though given ebooks I have discarded for poor writing maybe they should.
Submit also requires a fair amount of ancillary artwork like a publisher's logo, series artwork, cover image, and so on, and it looks like the title might not be approved if some details are missing. Again, this is more nitpicky than other services but perhaps it will lead to higher quality.
And then there's the money. ComiXology only pays the author half of the net income. For example, sales via the comiXology iPad app will net the author 35%. First Apple's vig is subtracted and then the remaining 70% is divided between coniXology and the author. Payments are made on a quarterly basis.
Not exactly a good deal, is it? Can anyone recommend a better option?