Reading safety data sheets helps on inks. Sometimes, solvents that are hazardous get changed over to more benign substances. Stuff like pigments, stabilizers, flow agents and so on are also important. Some inks jet at higher temperatures or voltages, or require different heads. Sure, most of the formulation between the same types of ink will be largely the same. However, some inks with even slight differences can cause major issues if mixed. Some inks have adhesion promoters and wetting agents that can cause major issues if left in a system that has incompatible ink already in it. Things can get even crazier when you get into UV and oil inks as well, lots of potential with incompatibility. That said, I think good aftermarket ink manufacturers can have ink as good as or better than OEMs. More aftermarket vendors in the UV ink space would be nice, but solvent inks are a crazy competitive field. Some more aqueous pigment inks are nice too, but there's not a ton of demand for those it seems.
