I don't think the glass is any better, they are not using ED glass for example in the Airmax range.
Similarly the tube and turrets look the same too.
The primary differences are :

1. The Airmax has the AMX reticle which is excluded from the vantage range.
2. The number of lens coatings - Airmax has 16 layers vs Vantage that has 11 layers.

For me : I don't like the AMX reticle and the lens coating difference is imperceptible to me - but maybe if you're shooting well into dusk perhaps you may see an advantage?

But on the other hand if you use NV maybe this is also a disadvantage - as I was reading something that suggested more lens coatings could degrade the image?
But I could have that totally wrong...