Six months of spreadsheets on two markets, and I still can't name the risk

Price it by asking what happens if it goes to zero, and how long you'd have.

In B, no ordinance means the county could adopt one, and a small county that suddenly gets 60 listings and a few loud complaints often does. Grandfathering is common and it is not guaranteed. So underwrite B twice. Once nightly, once as a long-term rental at whatever a three bed rents for in that town, probably $1,300 to $1,500. If the long-term case covers debt, taxes, insurance and a reserve, the ordinance risk costs you upside and doesn't cost you the property. That's a survivable position and at $210k it's plausible.

In A, run the same test and it fails badly. Nothing rents long-term for enough to carry $460k. So in A you're buying an asset whose debt service depends on a nightly calendar in a market where listings grew 31% and the top half holds low 60s occupancy. Note that the average you quoted is for the top half. Find the median across all listings and use that, first year you're not in the top half.

The permit premium in A also means you're paying today for a rule that a council can change, and you have no recourse if they do.

On occupancy in B, high 40s with summer weighting means your July and August carry the year. Model a rainy season or a summer where the lake is low.

Mostly lost in this room but the thing I noticed: in A you said permits change hands with sales in some cases. What decides the cases? That reads like the difference between an asset you're buying and a hope you're buying, and I'd want to see the ordinance language rather than the agent's summary.

Cabins in a mountain town at 60% occupancy get used hard, and $420k of purchase price says nothing about what shape the building is in. I'd have a real inspection on the roof, the crawlspace and the water system in either market, and in B, if it's a lake house on a well and septic, budget for the septic being older than the listing photos suggest.

On your actual question, @sextant's two-underwriting test is what I'd do. I'd add that in B you should read the county planning commission agendas for the last year before you decide nobody's thinking about it. That's public and it takes an evening.