[davidad_]

FWIW, I do find Interface to be subjectively noticeably more pleasant than Roboto in the comparison here.

[jack_jennings]

The comparison is not great for objective comparison—the metrics of Interface have been changed so that 11px =/= 11px from one to the other… this was the best approximation that I could get in-browser. Usually you'd want to set the two typefaces up so that the x-height is the same, and in this case Roboto is probably slightly larger still, and hence a bit darker in overall color.

[rasmusfabbe]

Actually, I think you want to compare apples & apples, meaning Font A and Font B at the same size and line height.

[lucaspiller]

Also subjective, but at that size on my machine (13" MBA, non-Retina, El Capitan, Chrome), I find Roboto is a lot easier to read. Interface looks 'greyer' and the contrast isn't so good.

[TuringTest]

While not the intended use case, I find Interface to be surprisingly readable at extremely tiny font sizes (7, 6, and even 5!).

Sure, you shouldn't be designing an interface with those sizes, but it may be something to consider for some zooming interfaces (primarily maps with lots of tags: street names, POIs, etc.)

[brusch64]

For me it was the other way round. Roboto was much more compact and easier to read. Interface seemed to use more whitespace in the words.