I don't think Gula Matari is an especially "jazzy" -- as in jazz solos -- sort of record, even though the band is stocked with ridiculously good soloists and there's some terrific soloing. The music is fundamentally about Quincy's skills as an arranger.
It's been a long time since I listened to Walking in Space -- but I think both records work similarly. Both are reminiscent of his soundtrack work as much as they're about "Jazz."
For example, the way Quincy re-imagines "Bridge Over Troubled Water" as something coming out of a southern church reminds me (at times) of his music for In the Heat of the Night.
In any case, it's terrific music -- even if it's more about vibe than about soloists. And, while I'm listening, Quincy can (and often does!) make me think things like: "Damn, the way Q blends those four trombones togther sounds soooo good! Is there a bass trombone in there?!?! Because I've never heard nothin' like that!"
I suppose I didn't answer your question! I'm not sure which record I prefer more or which is jazzier. I'd need to revisit Walking in Space.
EDIT: I just finished re-listening to Walking in Space. My impressions: Gula Matari is a more ambitious (and more interesting) record; it aims much higher than WiS. Quincy wrote "Gula Matari," a 13-minute long piece inspired by Africa for the album. There's nothing comparable on WiS.
So Gula Matari . . . less pop vibes. More ambitious in scope. Not necessarily more jazz (well, maybe some more), but a better, more satisfying record -- in this listener's opinion.
My 2 cents.