What are the differences between a pentamirror and a pentaprism in DSLR cameras, and how do they affect the overall performance and image quality?

A pentamirror is lighter and less expensive than a pentaprism, but it may result in a dimmer viewfinder image and slightly lower image quality due to its design. A pentaprism, on the other hand, provides a brighter viewfinder image and better image quality, but is heavier and more costly. The choice between the two can impact the overall performance and image quality of a DSLR camera.