Moorer had a shaky chin at Heavyweight unlike Usyk who has an iron chin plus Moorer was considerably past his best. Tua was made to look pedestrian by the likes of Rahman, Maskaev. Tua would never consistently get close enough to Usyk who would run rings around Tua all night long. You also mentioned a Southpaw in Moorer but also forget another tricky Southpaw in Byrd beat Tua pretty comprehensively.
It'd be a more competitive fight than people think, but I'd have Usyk winning on points. Tua was part of a crop that has nothing on this current list of B-rate operators that Usyk has breezed through with complete ease. If Breidis can take rounds off him, then a relentless come-forward fighter with an iron chin and major KO power would have some success. Tua won a medal at the world amateurs, too, but he gets this unfair label that he was too one-dimensional. While he was too crude against the likes of Lennox, he was not as crude as Chisora is, and he was more skilled, more powerful, and had a much better chin. If he was firing on all cylinders he would 100% be a problem for Usyk, I'd still back Usyk to win though.
Moorer has one of the weakest chins of any champ, Usyk the best. Usyk is also a great deal faster. Usyk wins most of the rounds but he knows he's been in a fight.
The version of Tua that went to war with Ibeabuchi would beat the hell out of Usyk,and stop him best version vs best version at heavyweight. Usyk wins only against the lackadaisical version of Tua, which we saw far to many times.
Best Usyk beats best Tua for me, competitive but wide. The Ibeabuchi fight was only such a great fight because both men chose to fight that way. Usyk would not. He'd have Tua off balance the whole fight, not let him set his feet, and win a wide decision.
I'm not one of those that thinks Usyk beats the entire 70s division blindfolded, but yes he wins this fight completely.
Yeah this screams quite clearly an Usyk decision. Tua could win a few rounds though but the skill level is too wide in the end. Decent fight though.