I am just about to have a 3 phase 30kva diesel generator installed on our farm for backup power. Multiple people had asked me, why not get a big battery? I honestly hadn't thought it was a viable option. Not sure. I want to power two houses in middle of summer or winter (-2 to 45 degrees C range). Power outages can last up to 24hr.
If you plan on keeping the same quality of life/not thinking about what kind of power you're using, go with the generator.
If you're ready to make some sacrifices/be a lot more conscientious with energy use, take the battery capacity you think you need and then double it.
Air conditioning, heating, stuff like microwaves and electric cookers, dryers, etc consume an absolute ton of power, and I imagine you'd have even more high-power appliances on a farm.
