I switched from Sunset Matte to "Production Matte" and I see no difference on-print. It's less expensive, stretches easier and looks the same.
The "Production" canvas appears to be all or nearly all synthetic material and is thinner and lighter than than Sunset Matte, but once it's stretched on the frame, it is indistinguishable from the thicker material. It shows no stretching or sagging issues after a year.