Question: Should I submit to a publisher or only publish on Kindle?
Really crappy answer #1:
If you can get published via publisher, it is always better. The reason is that,
1) you automatically get support for editing your book from publishing house,
2) most importantly you became “validated” author as, most times self-published Kindle authors are not considered professional, because everybody can publish with Kindle even if their work contain plenty of grammar mistakes.
If your book is fictional book, you have less chance to sell your Kindle ebook if readers don’t know you (for example from your blog page, twitter account and etc.) .