Under sink water filters are installed under the sink and send water through a pipe. It also uses its specific faucet. This system helps filter large amounts of water and doesn't take up counter space. However, it's expensive and requires modifications to plumbing, which can be equally costly.
Faucet filters are made with built-in filters that are then installed in your kitchen sink. It allows you to switch between filtered and unfiltered water with ease. It's also expensive and requires expert help for installation.