IMO the squat is more important to help grip on a launch as it induces weight transfer..
Weight transfer and half a tyre will give more grip than a full tyre and no weight transfer.
Obviously full tyre + weight transfer is best of all.
i put it down to new tyres why my grip was much better but now youve said that could well be the little bit of squat. car didnt squat at all with old springs and always lost traction in 2nd in the dry.