The only advantage of buying an album via download from Qobuz versus streaming it is that you now own the album. This means you can still play it if you cancel your Qobuz subscription, or if Qobuz loses the contractual right to stream the album (this does happen periodically with some labels and artists.) And, with a downloaded copy, this also lets you burn it to CD for use in your car or take individual tracks off the album for use in a "mix tape." The latter item used to be more of a thing than it is these days, I think.
Some people are more obsessive than others about owning copies of albums; that's something you need to figure out for yourself.