Bigger rod is higher pitch which is less turns for same movement which equals a lower turn speed of the rod and less whipping along with the added stiffness…
Yes I am very familiar with ball screws and acme screws. I buy them all the time from China.
I build and service CNC routers, 3D printers and co2 lasers full time. This however is my search for a very low cost machine that does not need the China imports.