A physical fence allows for physical holes — either through or under. Those holes would require a lot of manpower to find and repair. A hole in a fence can be made to be invisible except from very close up.
If somebody is spotted when they are 9 miles away — and agents dispatched to intercept them — they will never get a chance to damage a virtual fence by taking out cameras and radar units.
A virtual fence can never be as effective as a physical barrier if it comes to large numbers of people rushing through, but I would guess the manpower and maintenance costs of a virtual fence would be lower.
Now, if each of those posts was also a roosting point for a UAV armed with guns or tasers, I’d like it even more. It’s about time we got some benefit from our kids’ addictions to video games.
Best of all might be a physical fence with the electronic surveilance and UAVs to prevent anyone from messing with the fence.
Holes in a barrier - even big gaping holes in a concrete wall - are inexpensive to fix. If the wall system has an inexpensive visual monitoring system, those holes can be found in short order. An even less expensive method of detection would be to implant wires in the concrete (or Stormer fence) which trigger an alarm when the wire is cut or displaced.
A virtual fence is a fence in the same manner that virtual reality is reality.
I think you have that exactly backwards: the physical barrier, once completed, will cost less on an annual basis to maintain than no fence with the "virtual" setup which requires an agent going out and physically capturing every single person who the high-tech system detects as crossing the border.
And what happens to such a person who is so caught? Well, they just get sent back over to the other side of the border, so there is no reason to think that a virtual fence will not be constantly tested in many places.
And as to the "large numbers of people rushing through" that is exactly the problem that needs to be solved. We don't need to bring the number down to zero, we just to need to greatly reduce the number. Some people seem to make the argument that anything that does not guarantee zero people crossing the border is not worth doing.