I wanted a 1950's ZZ machine from Japan. Gorgeous automotive quality Toyota paint on the heaviest sm here, a 65 year old Morse. No complaints about cost or stitch quality, even if it has a single plastic gear, on the ZZ cam, that might fail before it is a hundred years old.
But, does this end-loader handle Tex 70 thread, the way some other SS and end-loader ZZ machines from the era do, pretty easily?* Not so far, not for me, with several bobbin cases tried. Of course, many or most newer home machines have not been designed for even medium thread, ever.
So, it is all in the design of the machine, especially the bobbin case housing; and that is true even of true industrial machines.
*I've sewn dozens of loops and bound edges in straps with Tex 70 and Tex 105 bonded nylon and polyester thread.