How does parallel conductor transmission line compare to coaxial cable with a plastic dielectric?

Explanation

Open-wire line keeps nearly all of its field in air rather than in plastic, so dielectric loss is small, and its wide conductor spacing reduces conductor loss. Those effects make its loss per unit length lower than plastic-dielectric coax; SWR and Γ depend on the ratio of load impedance ZL to characteristic impedance Z0, and different line types can have different Z0.