i do not think weight factors into the quality equation . i have had heavy and light machines that were very well made with quality parts , both coil and rotary . i think it comes down more to design and balance . if a machine is balanced correctly you can get away with a little more weight without causing hand fatigue and in contrast if a machine is too light it is almost like you have to hold the needles in the skin which may not affect the sore or injured hand problems you already have but can cause others