Due to the fact that the DOM might be isolated, the styles are isolated too. The advantage is primarily the ability to use styles without knowing and disturbing any globally assigned styles. The disadvantage might be the reduced usability of global styles.
Style Behavior
A Shadow DOM may include both <style> and <link rel="stylesheet" href="..."> tags. In the latter case, stylesheets are HTTP-cached, so they are not redownloaded for multiple components that use the same template.
As a general rule, local ...
