Gigabyte Brix barebones
A barebones unit provides some ability to choose configuration. Thanks to mobile parts, noise is almost non-existent. Far more affordable compared to a fully grown HTPC. Super-small footprint; can be VESA-mounted to the rear of TVs, or hidden. Easy to install hardware, and to initially set up. Sometimes comes with a Windows license, dependent on manufacturer.
Far less powerful than the alternative. 4K streaming still dependent on hardware configuration. You tend to get less bang for your buck. It comes with limited built-in storage. Less thermal capacity compared to the alternative. Not as much I/O in comparison with the custom-built option opposite.