To help you decide whether flip up sunglasses or spring-fit clip on sunglasses are a better choice for your requirements, here are the relative benefits of each type.
Spring-fit clip on sunglasses are more refined in appearance.
The fitting mechanism is neat and unobtrusive and when fitted to spectacles the overall appearance is not dissimilar to wearing prescription sunglasses. In comparison, flip-up sunglasses have a noticeable central bracket and hinge mechanism at the top of the frames.
For comfort, the spring-fit type of clip on sunglasses is generally regarded as preferable...