None are private in the sense of nothing leaving your machine, unless the model is local. The meaningful differences are retention, training, and who holds the key.
This is one of the questions people ask before they pick a tool rather than after, which is the right order. The rest of the answers are in the FAQ.
A desktop AI agent for Windows, built in Auckland, New Zealand. It reads your files, runs your terminal and drives your browser. Billed per token with a free monthly allowance and no subscription. See pricing, the FAQ, or who builds it.