SCSS variables are resolved by the compiler before the browser ever sees the CSS, which makes them feel like constants in a programming language. Native custom properties are part of the cascade, which is far more powerful: redefining --primary on .card.danger automatically flows down to every descendant that reads var(--primary), with no extra selector multiplication. Custom properties also let JavaScript do element.style.setProperty('--primary', '#fff') for runtime theming. The one place SCSS variables still win is loops and arithmetic at build time; for everything else, native is simpler and more powerful.

Native CSS nesting reads almost identically to SCSS: indent a selector inside a parent rule and use & to reference the parent. The big behavioral difference is that native CSS requires the & in more places than SCSS did. Specifically, when the nested selector starts with a type, pseudo-class, attribute, or pseudo-element selector, you must write &:hover and not just :hover; SCSS treated bare :hover as & :hover (descendant), then changed to &:hover (concatenated) in newer versions, which always confused readers. The native rule is consistent: use & whenever you mean "the same element with this state". Browser support is good across modern engines, but ship a static CSS fallback if you must support old Safari.

SCSS mixins and Less mixins compile to inlined declarations, which makes them feel like template functions. Native CSS does not yet have a shipped @mixin, but the practical replacement is a base class plus custom-property variants: define defaults via var(--name, fallback) in the base, then have variant classes set the variables. For specificity management, native CSS now offers @layer, which is more powerful than anything SCSS provides: layers ordered later win regardless of how specific the selector is, so a utility class always beats a framework class without ever needing !important. Use SCSS today for arithmetic, color functions, and complex loops; reach for native CSS for variables, nesting, and layered cascade control.