I do not like what SOOW pure rubber does to copper when environmental temperatures of 30c are encountered over a long period of time. It takes years but shiny copper turning brown and purple is not something I wish to see. I blame the sulfur in the rubber for this. Also SOOW insulation exposed endlessly to sunshine UV or ozone will rot.
SOOW flexibility is superb but it's only fair to yank it's shorts down and expose its warts to scrutiny.
I have not done a price comparison between Marinco and POLAR wire but the latter is flexible to -55c
http://www.polarwire.com/pdfs/2-13.pdf