Phil Garland showed me around Hall Rigging (as it was then) in Bristol, Rhode Island. We were discussing Spectra and how you work with it. When I asked how to cut it, he pulled out a Swiss Army knife from his pocket and sliced cleanly thru the line, which was about 1/4 inch. I pulled out my Swiss Army knife. The only difference between them was that Phil's was a whole lot sharper!
I guess if you're patient, and willing to keep an edge on it, a steel blade will work. Some of the more exotic blades, like ceramic, may cut down on sharpening time.