The breakdown is that U1 seems great since you can FADC combo into it, but it doesn’t really matter since Cody does so much damage and stun otherwise. It takes meter and is otherwise slow as fuck, with the latter making it actually the shittiest possible response to a jumpin. Using it on punish is right out.
U2 is more situational, but comes out way faster. It’s absolutely worthless as AA (the 1-hit airdust is utterly NOT worth learning), but then again so is U1. However, it doesn’t require meter which Cody needs for wakeups, command throw escapes, and FADCing out of CU fuckups. It also combos out of what Cody should be about, which is his frametrap setups. It’s not what Ryu has where you can get an extra 300 damage off something simple, but otherwise it’s what you’d want an ultra to be: something big to punish a stupid mistake.
Moreover, if you can build 2 bars of meter so easily, then you might as well save it anyway; Cody’s super combos behave a lot like U1 combos, and do a shitload of damage. If you’re playing someone you can reliably save up 2 bars against, then you can just as easily save up full super. Then you technically have 2 ultras at your disposal against this obviously crappy hypothetical opponent.
It seems to be a pretty typical process. First you think U1 is great because you can combo into it, then you reach a midpoint where you don’t know which ultra to pick, then you move to picking U2 exclusively.