Sorry, the two options were nuclear vs. renewables + storage (batteries and hydrogen). I don't think very large methane storage makes much sense; where does the carbon come from?
Biogas is mostly better than fossil, but we should generate methane from H₂O + CO₂ + energy. It would be useful and quick way to achieve energy storage and decarbonization.
Biomass is fundamentally limited by the very low efficiency of photosynthesis, so that it requires very large areas. It should probably be limited to providing liquid transportation fuels and feedstock for chemicals.
Biogas is mostly better than fossil, but we should generate methane from H₂O + CO₂ + energy. It would be useful and quick way to achieve energy storage and decarbonization.