I use an e-file and honestly cant think why I would want to use a e-file on the natural nail.
I'm not talking damage, I've been to the young nails stand, had them show me the file they use on the natural nail and can agree that it is so fine that in a trained hand it won't do any damage.
But its all about timing. I can pick up my hand file and remove shine with it.
Or I can pick up my e-file, fit my natural file bit, remove shine then change the bit to the one I would use for shaping.............
So I use hand files for the natural nail, its quicker. I use a hand file to shape, because the way I've been taught to apply product I really don't have that much filing to do and I don't cut in a smile line, I use the reverse application method so it's not needed.
In fact the only thing I do use my e-file for is de-bulking on the re balance and for that my e-file is a god send I really couldn't manage with out it.