At my school, white-out is pretty much universally frowned upon

Ostensibly, if you use white-out for correction you permanently lose anything you have written unless you have the time/motivation/sanity to sit at your piece of work and scratch it off with something (i.e. a key, where you'll probably ruin your work as well /nightmare).
If I learnt anything from VCE English, it's that you chop and change essays based on previous ideas at various stages of critique by your teacher. Pretty much, I could (neatly!) cross out a whole paragraph that I was unhappy with, but seeing as it was still legible, my teacher could offer their opinion on the validity/placement of that paragraph or the idea therein.
English aside, white-out has no place in maths or sciences whatsoever.
Verdict: Crossing-out is superior.