I can't compare Iontec to the 3S hybrid since it's full poly. Unfortunately, I did not try OS/4S. I tested those strings given to me, and these were the two recommended hybrids from GG that I could make out of the four strings given me (I couldve done 5S/3S, but Pro/Gut is not a rec. hybrid while 3S/gut is). As I already know what I like and it costs a fraction of those, I'm going to stick with what I've got. I can get gut mains, Iontec Black crosses for less than the L-Tec poly hybrid. As it is, it's no coincidence that most reviews in here are hybrids. I prefer that feel, hence my comment about not preferring poly hybrids. I always tension the softer string a bit higher to try to get a more uniform string bed stiffness, coupled with the fact that they'll lose tension over the course of stringing.