Thats exactly it.Black if you're lazy, white if you want to be unique (and if it actually fit your parts well)
Secondary cooling is minimal to none in computer cases. And black doesn't absorb heat from the air faster, it absorbs radiation heat faster.
Black absorbs every colour from white light (All the frequencies). Thats why it heats up much more.
But with heat from the air, there is not difference.
If you leave your case in the sun, then it will heat up like no other...