Hello welder5354, a very basic and simple way to describe one of the possible benefits of the pulse process over standard GMAW would be to say that the weld can progress with a higher average amperage input and still be able to control the weld pool. From the theoretical end of this, picture a conventional GMAW process, particularly one that is being performed out of position, ie. vertical, horizontal, overhead, in order for this welding to end up with the proper profiles, penetration, etc. A much lower heat input would have to be used and in some cases this would not even allow for the welding to be performed correctly. Pulsing, in a simple explanation, allows part of the welding cycle to incorporate a relatively high amperage input and as the current transitions to the lower amperage input the puddle is allowed to freeze somewhat and the fluiditity of the pool is prevented from getting out of control and having excessive sag or other detrimental characteristics. Conventional GMAW at a theoretical setting of say 25 volts and 180 amps might yield a certain type of characteristic in a weld bead at a given travel speed. A comparably sized weld bead done with Pulsed GMAW might utilize a primary voltage of 32 volts and a background voltage of 22 volts which would yield an average voltage of roughly 26 volts and an amperage of say 220 amps(these are not actuals but somewhat illustrate the difference between the two processes), since this is pulsed it could very well give the operator a similar size weld bead, yet the travel speed might increase a considerable amount and the penetration might increase as well.
GMAW-P definitely has much more to it than the little bit that I described above. The various equipment manufacturers have done considerable work to make refinements and improvements to this process and almost all of them have come up with distinct variations that have led to both successes and failures. In the proper situation, there can be definite benefits to be gained from the process. I hope this has helped in some way.
I did want to include one other line of thought in regards to your comment on heat input. I believe Chuck Meadows could possibly shed the best light on this, however, I'm going to try to convey some information that I hope I have understood correctly. The duplex materials by the nature of their make-up, actually do better to some degree, with additional heat input during the welding process(to a small degree this could include preheats), the additional heat helps to minimize the formation of excessive carbide precipitants which can promote intergranular corrosion. If I got this part wrong, I'm sure that there will be plenty of others from the forum to correct me and I apologize before hand in that event.
Good luck and regards, aevald