Well hang on, the nuclear reactor generates power while the storage only.. stores. You have to include the (lifetime!) cost of the storage plus the presumably renewable energy source you're feeding it with. (Of course you need storage with both systems to cope with demand-side fluctuations, but you'll need a lot more with wind/solar to deal with supply-side fluctuations.)

Hydrogen underground, not LNG, but yeah.

For some simulations to help answer when those two options are best:

https://model.energy/

The model doesn't support methane generation.

Hydrogen is cool, but we should also be investing in efficient methane production. AFAICT it's not too hard to make and has immense advantages - existing transport, storage and use infrastructure and market as a heavily traded good. We can use it for most of our energy or carbon needs with today's technology and existing machines with no or easy modifications.

Hydrogen can be more efficient and probably simpler when appropriate but is more finicky, still needs research and will take a lot of time to ramp up.

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?

CO₂.

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.

> where does the carbon come from?

https://en.wikipedia.org/wiki/Biogas

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.