OP is a fukking casual
I can't think of 1 album where Andre outshined Big Boi.
On their quintessential albums, ATLiens and Aquemini, they both had their moments. Andre won on Elevators and Two Dope Boyz, Big got him on Babylon and Wailin. Andre was a monster on Return of the G and Aquemini. Big Boi shined the most on Skew it on the Bar-B and Y'all Scared.
Speakerboxx > The Love Below
You could tell on Speakerboxx that Big Boi was still finding his comfort zone as a single artist and he nailed it with Sir Luscious Left Foot. Working with George Clinton and Janelle Monae, he kept it funky and varied while maintaining what he brought to OutKast
Meanwhile Andre does a few remixes where he blows everyone away and suddenly he's the
much better of the two?
Now if you say, Andre is the more vivid artist, with the verses that stand out more on first listen, cool. I hear you on that. This is where casuals like the OP stop. And believe that Andre clears Big Boi. "All Big Boi talks about are Cadillacs and guns, Andre be spitting that real"

They both hit the same levels of technical expertise, substance and depth if you listen closer. Big Boi speaking about grief due to losing his aunt on ATLiens, or the difficulty of escaping the dope game on Aquemini, or teenage pregnancy on Stankonia...
None of this is talking down on Andre's resume with OutKast. He's a bonified legend in hip-hop based on those 5.5 albums (Idlewild

), and what he brought to OutKast was irreplaceable. The same applies to Big Boi. And with the difference in their solo careers, I've yet to hear a cohesive argument for why overall, Andre > Big Boi