Breadth, first and most obviously. ChatGPT is a general-purpose assistant and Melda is not remotely one. In the same session you can draft a sponsorship email, debug a script for your editor, plan a shoot, and argue with it about your own thesis. Melda does one job and refuses the rest.
Cost, second. The ChatGPT pricing page states that the free version is available to everyone, with paid tiers above it, as of this writing. Melda lets you start free without a card, but the ongoing plans are paid, at $19, $49, and $99 per month with 20% off annually. If your repurposing volume is genuinely low, the free general assistant is the rational choice and we would rather say that than pretend otherwise.
Control, third. Some creators want to steer every instruction, iterate line by line, and keep the whole process visible. An opinionated pipeline takes some of that away by design. If you enjoy prompting and you are good at it, that is not a bug you need to pay to remove.
And flexibility of format. If your repurposing output is not talking-head short-form — newsletters, threads, carousels, long-form blog posts — a general assistant will serve you across all of it, while Melda is aimed squarely at scripts you say out loud.