I think you’ll find that no-one’s answered this yet because on both platforms all the available RTF editors suck.
If you are prepared to work in plain text then your available options go up dramatically for both platforms. I use Editorial (on my iPad mini) and Draft (on my Nexus 5); both of which are excellent (multi)Markdown editors with DropBox support.
My best advice though will be to wait for Scrivener on iOS; that will support RTF and, as I understand it, will work directly the scrivener file format. From what I’ve read, Keith has bent over backwards trying to rich text editing to work above and beyond what the standard CocoaTouch APIs give developers out of the box.