What are the real benefits of Fieldbus systems over the conventional 2 wire technique? Please be so specific (use facts and figures) in your answer.

As an experienced instrument engineer and by comparing the conventional4 to20mA current loops and field bus technologies, I can say that In this newer technology, actually there is no cost saving regarding the reduced copper cabling considering the required length of the cables and its unit price. Also the number of the required JBs in FB system is definitely higher than the old tech and the JBs contain electronic circuitry which increases the unit price. I don't see any easier engineering in the FB system, and thanks to the progress in IT  and electronic industries actually the capacity of the new microprocessors is much higher that what we need in a DCS. But an undeniable fact that gives a great mark to the FB system is what Mr. Abdul Rasiq mentioned in his answer that states the capability of FB equipment to support the plant control system with definitely higher and more informative live data from the control and sensing equipment that enables the higher level system to use the data in maintenance strategies. I believe this is the main advantage of field bus equipment over the conventional current loop devices which has made an added value for this technology.

1.Easily configure and reduce junction box

2.to identify fault location

3.communicate more addition data

Control in the field,wiring saving,Reduced Engineering costs,Reduced workload for DCS.