Head-to-head comparison
Apertus 8B Instruct 2509 (Swiss Ai) and Apertus v1.5 8B (Swiss Ai) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.
Snapshot as of 17 August 2026
As of 17 August 2026, Apertus 8B Instruct 2509 holds the stronger ModelCap Index position (#161 vs #163); and Apertus 8B Instruct 2509 ships open weights.
Evidence: global corpus prior · leave-one-anchor-out calibrated · global corpus prior · leave-one-anchor-out calibrated. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.
Neither model has a published result on a public benchmark board ModelCap tracks yet.
Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.
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Apertus 8B Instruct 2509 ranks higher on the ModelCap Index as of 17 August 2026: #161 against #163. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.
At least one of the two has no listed API price on ModelCap right now, so no price comparison is made.
Both publish a —-token context window.
The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.
Apertus 8B Instruct 2509: Open weights. Apertus v1.5 8B: Gated access. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.
ModelCap currently lists 0 API providers for Apertus 8B Instruct 2509 and 0 for Apertus v1.5 8B, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.
Every figure comes from the sealed ModelCap dataset published 17 August 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.