Comment by sothatsit

OpenAI and Anthropic give you a lot of usage/$ through their plans. For the Anthropic Max plans, this can be like a ~90% discount. Copilot does not benefit from this (their pricing model is also different though, it is request-based rather than token usage based, so it is hard to compare).

That's not to mention that the models generally work better in their own harnesses, which is perhaps unsurprising because the models have been trained with the specific harness in mind (and vice versa). That said, I think some 3rd-party harnesses do a lot of work to make different models work well in their harness.