If you meant 3.5 9B and you truly believe it's as good as 4o then I can only assume you have a very basic use case.

(barring some breakthrough that reduces costs, which of course may happen, but for which recent model improvements are not strong evidence of)

"Reasoning" and now "Agentic" AI systems are not some fundamental improvement on LLMs, they're just running roughly the same prior-gen LLMS, multiple times.

Hence the conclusion that LLM improvement has slowed down, if not stagnated entirely, and that we should not expect the improvements of switching to these "reasoning" systems to keep happening.