I don't know. All of my faves have a different combination of the two. Rihanna has huge sales and moderate reviews. Iamamiwhoami has hardly any sales but critical acclaim. Azealia Banks has moderate sales and moderate acclaim thus far. And Sky Ferreira has neither, so...
If I had to pick just one:
Rihanna: Sales
Iamamiwhoami: Acclaim
Azealia Banks: Acclaim
Sky Ferreira: Sales