I use PVC for heavier coverings and for the poly covering in winter. Looks like this
It is less likely to smoosh with snow and distort w/wind. The wires are for protecting things in summer where rain and wind go right through. The exception is in the hoop house, when the poly is on and we are getting into the low 20s or lower, I’ll put row cover over the more tender plants so I can grow lettuces and other like things.