New language models appear every few months, and each one is presented as the best. For a product team the useful question is different: which model solves our task reliably, at a price and speed we can afford, without breaking our privacy rules?
Start from the task, not the leaderboard
Public rankings measure general abilities. Your product needs something narrower: classifying requests, extracting fields from documents, answering in a specific tone, writing code or reasoning over long texts. Collect fifty to a hundred real examples of your task with the answers you expect, and test several models on them. The difference between models on your own data is often very different from the difference in public tests.
Count the cost per request
Price depends on the amount of text sent and received. A model that is slightly better but five times more expensive may only be justified for a small share of complex requests. A common pattern is routing: a fast, inexpensive model handles simple cases, and only difficult ones are sent to a more powerful model.
Check speed and limits
For a chat or an interface where a user waits, response time matters as much as quality. For background processing, throughput and rate limits matter more. Test both under realistic load before committing.
Decide where data may go
Some data cannot leave your infrastructure or a specific region: personal data, contracts, medical or financial information. In that case look at providers with suitable data processing terms or at open models that can run on your own servers. Make this decision early - it often narrows the list more than any benchmark.
Avoid locking in
Models change quickly. Keep a thin layer in your code between the product and the provider, store prompts and test sets separately, and you will be able to switch or combine models when a better option appears.
The short version
Choose a model by testing it on your own examples, counting the real cost per request, checking speed under load and respecting your data rules. Design the system so that the model can be replaced.