@danderson The tl;dr:
Decision tree:
(1) Whole house; or (2) Critical subpanel.
I decided to go with 2, because I have some really awfully large loads I don't want to provision an inverter for: Two AC units (house is annoyingly geometrically complex) and 5kW of outdoor heaters that only get used about 5 hours per year, and an electric oven.
Once I'd decided on (2), it was a question of getting good runtime without needing to spend a ton on an inverter.
1/2