The reason AWB emerged as a defender in the first place was that he completely shut up Zaha in training when he was tested in the role (he was a winger/striker at that point, an attacker who had pretty much zero defensive awareness as such, he was just quick and oddly adept at tackling).
He's not a run-of-the-mill player in terms of his development.
Anyway, the reason he managed to neutralize Zaha was not that he was a brilliant defender (in terms of awareness, positioning and whatnot), but simply that he had the speed to shadow his man as - pretty much - a man marker...and, again, his tackling ability (which remains something of an anomaly, something innate or whatever one wants to call it).
This, in itself, is a potentially very useful quality: as a tactical option to have, it's brilliant.
It's clearly not enough to make him a default starter for a team with high ambitions at the highest level, though: as it stands, he isn't consistently good enough either offensively or defensively for that.
But if he can - say - establish himself as a reliably decent 2nd choice RB, then his extreme qualities (or rather quality, singular: it's the tackling) could be very useful in certain scenarios (where you want to neutralize or significantly reduce the impact of an opposition winger/wide player).
As for him versus Dalot, short-term: like I said in the other thread, keep 'em both for now.