I would think that metallic conduction is more efficient because:
1) Metal ions form a network, or clusters, that can share electrons pretty efficiently amongst one another. Electrolytes, in contrast, share charge via ionic conduction. And diffusion of ions (large atoms) is slower than electron diffusion- and in atomic timescales, we are diffusion limited.
2) Electrolytic conduction requires a chemical reaction, i.e. a change in state, of the initial compound. For example, in an lithium-ion battery, lithium graphite releases lithium ions (and electrons) at the anode. Here, electron conduction for this reaction is slower because there is no network to coordinate the electron transfer to solution.
3) It does depend on temperature. At higher temperatures, the metal conductivity decreases (see this chart for copper, for example: Thermal Conductivity: Copper ), whereas electrolytic conductivity increases because the bonds are excited.HTH