First of all, how does 428hp on 180mm^3 of fuel not mean better BSFC? I have never seen stock injectors make more than 300 in person and 340 I have only heard about The truck that made the 340 is running my exact same turbo, and more timing than me. Stock injectors inject ~150-155mm^3 of fuel per shot at full stroke.
428rwhp divided by 180mm^3 yields 2.37hp per cubic millimeter injected.
340rwhp divided by 150mm^3 yields 2.26hp per cubic millimeter injected.
Droplet size is bigger.......from and orifice of .006" to something LESS than .007" I don't think you can tell me that will effect droplet size, or more correctly, the surface area to volume ratio of the droplets a discernable amount. Injection pressure remains the same, it is not a fixed flow through the nozzle, it is a fixed pressure (assuming flow rates through other parts of the injector are not exceeded).
These are unit injectors. HEUI. Hydraulic Electronic Unit Injection. As long as flow is maintained throughout the hydraulic circuits within the injector, nozzle enlargements do not drop injection pressure. And I will assure you, that a change of less than 1 thousandth of an inch does not drop IP.