Tough call.
But imma go with Brook.
Shanks control over time and space will definitely prove a problem but Brook will easily counter it with his powerful God tier Haki.
And once Brook goes Satan Mode then its all over Shanks.
Brook while in Satan Mode already massacred Kaido and Mihawk so no way in hell Shanks can survive it.
Plus Brook can use "Call of the Dead" to summon people like Roger,WB and even the all mighty legendary Ace to fight along side with him.
Tbh the only person I see beating Satan Mode Brook is Doflamingo since the manga confirmed Doflamingo is the strongest.
I must be missing something here. Since when did Shanks have control over Time and Space? I don't recall Brook's "Soul Mode" being used against anybody but Big Mom's Homies, who were at a natural disadvantage because they're empowered by souls. Brook IS a soul, returned from the dead. So unless I missed the point where Brook was named the fifth Yonko, going up against Shanks is suicide. Kizaru, a Marine ADMIRAL, opted to not fight him. You must be joking if you think this is even close to a fair fight.
Final Score- Shanks: 7, Brook: -0
Or are we playing the "hypothetical scenario where everything goes" game?