Any reason to create pre-KF8 e-books?

I have a book that does not really take advantage of any advanced KF8 formatting. Would I benefit from creating a “lean and mean” prc file for this book? Or it will be converted to KF8 anyway, once uploaded to KDP?

I tried side-loading prc files to Kindle Fire, and Kndle Fire displays them no problem. Not sure about Fire-HD.