There’s not much of a difference for most usage scenarios. 20 minute import doesn’t matter since you only do that once.Performance wise they basically don’t have any differences (Sphere rendering performance is relatively the same due to shaders). The Sky Sphere seems to get more love and by UE4 default stuff - see this day/night tutorial which relies on the default sky sphere:
But in the end - if you believe in the box then use the box. Nothing wrong with that.