Origin and test environment
The conclusion is first: after four rounds of testing, both models have their strengths and weaknesses in "speaking human language". Claude Opus 5.5 is better in terms of sense of proportion and "non-fabrication" of SMS messages; Longer articles in Gemini 4 Argon are smoother, but the default writing style is heavy. Neither of them escaped the AI-driven tone when it came to writing long articles.