but he's an incredibly lackluster military tactician. His "genius" plan of defeating the Soul Society involved wiping out half of his army, just to trap four captains in Las Noches.
The way I see it, the sole use of the Espada was for them to die while weakening the Captains. They were never meant to kill them. If they did, all the better, but them dying didn't really change anything. Sure, that's arrogant of Aizen, but ultimately the only reason he lost was because he a)didn't kill Isshin and Ichigo (and Urahara) while they were lying helpless on the ground AND b)destroyed the Kototsu AND c)didn't retreat when he realised Ichigo was stronger. Notce how I said AND. If he hadn't made even ONE of those mistakes, he'd have been victorious.
He was exposed heavily during the Deicide arc, which revealed just how much of a spoiled brat he really is.
I'm not sure what you mean by exposed... :
By contrast, Yhwach managed to outwit Yamamoto himself, tricking the dude into using up his Bankai on a decoy, stealing Ryujin Jakka and killing him for good.
Yamamoto himself? Please, the old man was borderline senile... And he didn't use a decoy, he used a friggin' power-cloning Quincy. "Same" thing Aizen did with Extinguir. And the only reason Aizen didn't kill Yama after his sacrificial kido was because he thought he was already dead. Sure, the theft of his bankai is something commendable, but it's not like Bach built the stealing badges himself.
I'd say Yhwach was ultimately smarter.
More practical, yes. More direct, definitely. But smarter, no.