Putting it simply there is a trade-off between field of view (FOV) and comfort.

Our 6mm foam replacements offer a better FOV bringing you closer to the lenses for a more immersive experience however this results in less comfort. The 14mm foam replacements are designed with comfort in mind, FOV will be the same as using the original HTC Vive foam but our memory foam offers a much more comfortable experience. 

The two sizes are equally as easy to clean. Simply wipe with anti-bacterial wipes between uses and you're good to go. If you are using glasses we recommend the 14mm model which allows extra width for your frames, and doesn't bring them too close to the lenses.