The general trend -- naming models classes after objects from some implicitly ordered set -- was started by Anthropic. It's generally fine, but they didn't leave enough headroom for their largest models, so the implied ordering for opus/fable/mythos is kind of muddled to the average person.

Small/medium/large/etc. has the most easily deducible ordering, but it's not great from a marketing perspective and also has headroom issues unless you're ok with names like gpt-8-xxxxl.

OpenAI's naming is probably the best. The ordering is easily deducible and there's plenty of headroom in both directions. Tons of cool sci-fi sounding names still on the table, and it also comes with the implication that they're approaching a singularity.

I don't know what Google is doing. It's kind of impressive to have an inconsistent ordering after only three names.