Gas all the way. Electric rates are higher, and electric requires a much larger drop service to the home than a standard service panel.

I don't have tankless but I highly recommend gas if you are in a vicinity that tends to lose power ... we have lost power for days sometimes in snow/ice/rain storms and having hot water even though no heat (we have no generator) really helps keep the place inhabitable.

Natural gas units are the way to go. I would strongly suggest you have a consult with the local gas company as to; how many units you will need / will you need a recirculating pump / placement of units (they will need yearly servicing). The calculations necessary for a good install are best done by the gas company.

We have gas. Wherever we've lived, it's always been cheaper.

The OP has SOLAR PANELS....she will produce her own electricity. For me that makes electric a no brainer. Free electricity = electric everything.