NWA has to be the most important.
like
@DaveyDave said, Wu clearly has more classic songs/albums (than Outkast) if you count solo albums. then again, just for arguments sake... if you count NWA's solo albums this becomes a completely new debate too. But I understand there's a difference between those & Wu solos because Wu damn near treated the earliest solo albums like they were group albums.
Outkast has 4 dope group albums though & imo that's more than Wu has, I'd say they have 2 dope group albums and rest of em are pretty good... but not really that close to the level of Enter the 36 Chambers or Wu-Tang Forever.
I'm gonna say that as a crew/collective Wu > Outkast. But if we're just counting 'official' group albums/appearances Outkast > Wu.
But like I said, if we take Cube's/Eazy's/Dre's/Ren's & maybe even DOC's solo material. then it hast to be NWA. But it really doesn't make sense since most of those albums were made when NWA didn't exist anymore.
Wu's debut is probably my favorite album of all 3 groups though. Either that or ATLiens.