They look exactly the same.
I looked around in Google's FAQ, but couldn't find anything about it.
Is there supposed to be a difference?
Some simple google search gave me the Guidelines for using Noto, and in there you find:
For an Arabic website that needs to use an UI font for UI elements, such as buttons and tabs, that have more strict vertical space.
The design of Noto UI fonts are adjusted to be more vertically compact, a refinement made for user interface typography.
The FAQ on Github has more information (currently missing from the website):
The UI fonts were initially prepared for use in Android’s UI. They have tighter vertical metrics, and some glyphs that would be clipped are redrawn to fit within the constrained space. They can be used anywhere that has limited vertical space. There are no UI verions of scripts that do not need such adjustment, and the non-UI versions should be preferred for use in body text.
So, use the UI version in places where it would look strange if the text were to extend beyond the boundaries of the UI element.