What elements do you want to draw the user’s eyes to on your platform? Is it one, centralised component, like a contact form? Alternatively, is your content more varied (like a product page)? The answers to questions like these should also factor into your decision between a light or a dark UI.
Let us revisit the Spotify example – its darker interface allows for more comfortable viewing in more dimly lit locales, such as a party or a dinner. So why does its primary competitor, Apple Music, utilise a different technique?
The first reason may be purely brand-related (Apple loves crisp white interfaces), but there is a usability factor as well. Apple’s UXers want to emphasise the platforms’ diverse colour elements, namely, the album art.