ChatGPT is a general chat AI. You ask, and it writes: post ideas, captions, scripts and hooks. It can make images too. Its plans run from a no-cost tier with limits, through Go at $8 a month in the US and Plus at $20 a month, to Pro from $100 a month. For writing, that is very good value.
VEXI (formerly Social Realtr) is an AI content studio that runs social media for entrepreneurs and creators. You describe what you want and it makes the posts, videos, designs and captions, then schedules and publishes them. Plans start at $199 a month, and every plan starts with a 15-day trial.
The difference is what happens after the words. With a chat AI you copy the text out, film or find the footage, cut it in an editor, add music and captions, pull stock clips, then load it all into a scheduler, or wire in plugins to do some of that. You are the one stitching it together. VEXI is service as software: you ask once, and the post comes back written, designed, edited and scheduled. VEXI costs more than ChatGPT: plans are $199, $399 or $599 a month. What you pay for is the work you no longer do.