What is the difference between Standard and Advanced?
Both return listings. Advanced also gets Insights, aggregated market data, which is coming soon. Both cost the same.
Standard covers GET /v1/properties: published listings with every property detail in the reference. Advanced covers the same endpoint and will add the Insights endpoints under /v1/insights, which return aggregates by place and period. Insights is coming soon and not live yet; Advanced customers get it on the same key as soon as it launches.
The two tiers cost the same, so the choice is about what you need rather than the price. See “How much does the Housing Market API cost?”.