Digital BW, The Print

I would say that I'm not at all surprised that there was a difference between the inks. I  bet you even get differences like this between different batches of Epson inks.

As I understand it, the HEAD ID tells the processor how high the drive voltage should be for pigment or dye ink (remember back when you had a choice) and probably the frequency of the pulses (or maybe duty cycle) to drive the piezo. Both of these things will change the way a certain ink will spray, and of course small variations in surface tension, viscosity, and probably about a dozen other factors will affect the spray pattern.

Also this should be no surprise as I thought this info about head ID was known way back when people were putting different inks in the 1120 and 1200 printers. I seem to recall a little talk about fixing issues by changing the values in the ID string.

I'm not real concerned.