What's the best OpenAI model for the most human-sounding outputs?

I’ve been experimenting with different models for content generation and noticed significant differences in writing style, tone, and readability. Some models seem to produce outputs that feel more natural and conversational, while others tend to sound overly formal or have patterns that make the text feel obviously AI-generated. For those using the OpenAI API for long-form content, marketing copy, blog posts, or general writing tasks, which model have you found produces the most human-sounding output with the least amount of post-processing?