This is simply not true. Your heuristic is broken.
The recent Gemma 3 models, which are produced by Google (a little startup - heard of em?) outperform the last several OpenAI releases.
Closed does not necessarily mean better. Plus the local ones can be finetuned to whatever use case you may have, won't have any inputs blocked by censorship functionality, and you can optimize them by distilling to whatever spec you need.
Anyway all that is extraneous detail - the important thing is to decouple "open" and "small" from "worse" in your mind. The most recent Gemma 3 model specifically is incredible, and it makes sense, given that Google has access to many times more data than OpenAI for training (something like a factor of 10 at least). Which is of course a very straightforward idea to wrap your head around, Google was scrapign the internet for decades before OpenAI even entered the scene.
So just because their Gemma model is released in an open-source (open weights) way, doesn't mean it should be discounted. There's no magic voodoo happening behind the scenes at OpenAI or Anthropic; the models are essentially of the same type. But Google releases theirs to undercut the profitability of their competitors.
This one? https://artificialanalysis.ai/models/gemma-3-27b