AC and DC power lines both loose energy to resistance.
AC power looses energy in another fashion due to capacitance and inductance called reactive power.
By using superconductors (0 ohm resistance) for the power lines, you eliminate all losses for DC, most losses for AC, and introduce new losses for the cooling equipment.
Of course, with superconductors the formula isn't as simple as V=IR because then you could get infinite current. (V/0 = I) With superconductors, there is a maximum current density (Amps per m^2 as the area of the cross section of the wire) before the wire starts to produce resistance.