When to use the required attribute vs the aria-required attribute for input elements?

When John Foliot wrote that article in 2012 it was very much true. You needed both.

Today that is no longer the case. I can take your example, put it in a CodePen, and check it in JAWS and NVDA (sorry, no VoiceOver today):

<label for="textbox1">Input</label>
<input id="textbox1" type="text" name="Text Box" required>

You will be happy to know that both NVDA and JAWS announce the field as required.

In short, you do not need aria-required any longer. Just use required.

You can read a bit more about the ARIA attributes you can dump in this article by Steve Faulkner (one of the editors of the ARIA spec) from 2015: http://html5doctor.com/on-html-belts-and-aria-braces/

HTML5 now has the required attribute, but aria-required is still useful for user agents that do not yet support HTML5.

Ref: Using the aria required attribute post on MDN