Well you have to think about this, without the shield juggernaut is still COMPLETELY invulnerable. Theres next to nothing that has ever pierced his skin UNDER magic.
This would be a hard match up for thanos even without the shield because you have two powerhouses and one of them has unlimited strength and is invulnerable against a being of unimagine power and durability is incredible but not on juggernauts term. The thing that would decide the ending of this battle is if thanos has enough power to get past juggernaut durability. I know for a fact that he wont be able to get past the shields.
This is basically a battle of whos stamina is greater and with that, I give this battle to juggernaut. Wolverine claws has seemed to pierce everyone in marvel comics, even the great odin but fails to get past juggernaut durability.
Good fight though.