The other advantage of aluminium is NVH reduction and rigidity
Alloy castings bend less than pressed steel when driving hard. The cast steel arms on the GTI are actually far better than the cheesey pressed wishbones the poor old MK7 and MK8 are afflicted with. They're just heavy.
The Passat alloy knuckles widen the front track a little as well. With the whole compliment of alloy parts and decent suspension, ARBs etc, the cornering is quite impressive