In chess games between two computers, pondering makes sense only if the competing chess engines use separate processors or cores. If they share the same core, the pondering program steals half of the time from the program thinking in the normal way and uses the stolen time less effectively.

Are there any real net gain benefits for enable pondering if they share same cores?

In my case i have 16 threads available at disposal. PB = on means 8-threads each. In other words 50% reduction in processing power for each engine.

Nope, there are no net gain benefits whatsoever.

In this case sacrificing speed & depth for increased time. 

"It is still an exercise in futility. Let's say the move prediction is 50%. Both of your engines would still be reaching the correct response line half of the time in the time control and in the other half will have wasted considerable time finding the wrong move for nothing to gain from it at only half of the potential depth. Your engines might agree on the same predicted reply at 15ply for example but may change course once 30 ply is reached. An exercise in futility."

"Permanent brain question"???

How about dual socket motherboards and two identical CPU's 

Let say each cpu have 8 cores (16 in total)

8 cores can run continuously with pondering enabled. Versus 16 cores each turn. 

I will ask over there surely