What exactly may be the difference between the 4-20 mA output signal in 2- and 3-wire technology? At Ease is answered best from the viewpoint of an individual: An output signal in 2-wire technology means:
less wiring required
better EMC protection, since interferences can be filtered more easily
better protection against wiring errors
The only benefit of 3-wire technology is that higher ohmic loads are possible, i.e., the existing loop can be operated on a measuring instrument of relatively high input impedance. Conclusion: Apart from a high ohmic load requirement, 4-20 mA in 2-wire technology supplies the user clear advantages- also over other signals, such as 0-10 V.