Updating CSS transform has the least impact on rendering performance because: 1) It doesn't trigger layout/reflow operations, 2) It can be hardware-accelerated using GPU, 3) Only requires composition, which is a cheaper operation, 4) Doesn't affect other elements' positions or dimensions. In contrast, changing dimensions or position requires layout recalculation, and modifying text content might require both layout and paint operations. This is why transform is preferred for animations and dynamic visual changes.