We've discussed getting backup power periodically since moving (most of our neighbors have something). After the big bomb cyclone that hit the NPW this became a priority and I did a very similar tradeoff matrix.

Here were some of my consideration points against a generator (I had a list for batteries too):

1. the previous owners electrified the house so having a tank just for a generator didn't make sense

2. per 1, a small tank wouldn't last very long and if we're out of power for multiple days gas delivery is unlikely to be happening anyway.

3. tank + generator didn't have a practical placement location for us

4. smaller portable generators didn't make sense from a maintenance perspective since they didn't auto test.

5. what happens if it fails a self test right before a storm?

6. we get intermittent power cuts / fluctuations / outages throughout the year and the generator + ATS wouldn't protect sensitive electronics well

Edit: ATS + batteries can play nice together then I might look at doing a small portable as aux backup