Yes, the books converted from Sigil output by Calibre are good on the Kindle. I've got quite a few texts I've done that way.
One thing that .epub has that .prc / .mobi doesn't support is multi level TOC's, that is links to "chapters" underneath broader links like divisions. For instance I took a King James version of the Bible in .epub and added an OT and NT link with the books from each division under each major heading. Looks good in .epub but in Kindle readable format they all appear flat and there is no benefit to the upper level links.