Well it depends on what you want to do with it mate. I use 1.5mm stein for making ultralight soft shackles and other splicey goodies but for guy lines i use spectra as its not as slippy at the PU coated dyneemas and takes a knot better. If using with dutchware i always go with spectra now as its tighter weave is more abraision resistant.
What you planning on using it for?