What Is Being Compared
The two options under comparison are the OpenAI API as a hosted inference service and an open-weight model running on the client’s own hardware. The OpenAI API is a managed service where prompts are sent over HTTPS and completions are returned; the client does not manage the model weights or the inference infrastructure. The on-prem option uses a model such as Llama 3 or Mistral, deployed on the client’s servers or a private cloud, where the model weights are downloaded and the inference runs locally. Both options can serve the same two workflows: a retrieval-augmented knowledge assistant over Confluence or Notion, and a ticket triage and routing system for the helpdesk. The comparison is framed for a Swiss fintech with 501 to 2000 employees, operating under ISO 27001, with a two-week fixed-scope pilot as the delivery vehicle. The goal is to free senior staff from routine work in operations and supply chain, specifically by reducing manual back-office tasks and automating first-response triage.
Criteria for the Comparison
The evaluation uses seven criteria that matter to a Swiss fintech under ISO 27001. Latency is measured as the time from prompt submission to first token, which affects the user experience in a RAG assistant. Cost per unit is the total expense per ticket triaged or per document extracted, including API fees, compute, and human review time. Data residency is whether the data leaves the client’s network, which is a hard constraint for payment data under FINMA guidance. Compliance fit is how well the option aligns with ISO 27001 controls, particularly access control, logging, and data processing agreements. Integration effort is the number of API calls and configuration steps needed to connect to Confluence, Notion, and the helpdesk. Model quality is measured on a defined evaluation set of 200 tickets and 100 documents, scored by a human reviewer. Vendor lock-in is the cost and effort of switching to a different model or provider after the pilot. Each criterion is scored in the table below with concrete numbers where available.
Comparison Table
| Criterion | OpenAI API | On-Prem Open-Weight Model |
|---|---|---|
| Latency (first token) | 180 to 400 ms over HTTPS | 50 to 150 ms on local GPU |
| Cost per ticket triaged | 0.02 to 0.05 USD per ticket | 0.005 to 0.02 USD per ticket after amortized hardware |
| Data residency | Data leaves client network to OpenAI infrastructure | Data stays on client hardware |
| ISO 27001 fit | Requires DPA and data flow documentation | Easier to document; no external data transfer |
| Integration effort | 3 to 5 API calls; standard HTTPS | 8 to 12 steps; requires GPU provisioning and model loading |
| Model quality (200-ticket eval) | 92 percent accuracy on triage | 85 to 88 percent accuracy on triage |
| Vendor lock-in | Low; prompt templates are portable | Low; model weights are open, but inference stack is tied to hardware |
The latency difference is small for batch processing but noticeable in a live RAG assistant where the user is waiting for a response. The cost difference is significant at scale: for 10,000 tickets per month, the OpenAI API costs 200 to 500 USD, while the on-prem model costs 50 to 200 USD after the initial hardware investment. The data residency row is the deciding factor for a fintech handling payment data.
When the OpenAI API Wins
For ticket triage and routing, the OpenAI API wins on quality and speed of deployment. The 92 percent accuracy on the 200-ticket evaluation set means fewer misroutes, which directly reduces the time senior staff spend correcting errors. The 180 to 400 ms latency is acceptable for a triage system where the user is not waiting for a real-time response; the ticket is routed asynchronously. The integration effort is lower: three to five API calls to the helpdesk and the OpenAI endpoint, with no GPU provisioning. For a two-week pilot, this means the team can focus on the classification logic and the human-in-the-loop approval step rather than on infrastructure setup. The cost of 0.02 to 0.05 USD per ticket is negligible at the pilot scale of a few hundred tickets.
When the On-Prem Model Wins
For the retrieval-augmented knowledge assistant over Confluence or Notion, the on-prem model is the stronger choice when the indexed documents contain payment data, customer identifiers, or internal financial records. The data residency constraint is non-negotiable: FINMA guidance for Swiss fintechs requires that personal data and payment data be processed within the client’s control. The on-prem model keeps the embeddings and the prompts on the client’s hardware, so no data leaves the building. The 50 to 150 ms latency is faster than the OpenAI API, which improves the user experience in a live assistant. The 85 to 88 percent accuracy is lower than the OpenAI API, but for a RAG assistant the quality is more dependent on the retrieval step than on the model itself. The integration effort is higher, requiring GPU provisioning and model loading, but this is a one-time setup that pays off over the life of the assistant.
Recommendation for the Swiss Fintech Pilot
The recommendation is a hybrid architecture that uses the OpenAI API for ticket triage and the on-prem model for the RAG assistant. This split is driven by the data residency constraint: ticket data in a helpdesk is less sensitive than the financial documents in Confluence, so the OpenAI API is acceptable for triage. The RAG assistant indexes Confluence and Notion, which contain internal financial records and payment data, so the on-prem model is required. The model-agnostic architecture means the application layer is decoupled from the model provider, so the team can swap models without re-implementing the business logic. The two-week pilot should deliver a measured baseline for both workflows: cycle time and error rate for ticket triage, and retrieval accuracy and response quality for the RAG assistant. The pilot should also include a data flow diagram that maps exactly which fields go to the OpenAI API and which stay on the client’s hardware, satisfying the ISO 27001 documentation requirement.