Vanilla JS vs Vue.js: what is the difference in application architecture?

Vue's architecture centers on Proxy-based reactivity that auto-triggers re-renders; Vanilla JS updates the DOM only through code you write by hand.

Both end up changing the same DOM elements, but they get there through different mechanisms, and that changes how an application is structured from the start.

When does Vue's reactivity model pay off?

Once a view depends on many pieces of state that change independently, such as a form with live cross-field validation or a dashboard with filters affecting several panels, Vue's dependency tracking re-renders only the affected parts automatically. Writing that same tracking by hand in vanilla JS means explicitly listing, for every piece of state, which DOM nodes depend on it.

When does direct DOM control fit better?

For a page with one or two isolated interactions, tracking exact dependencies by hand is simple enough that a virtual DOM diffing cycle adds a layer of work without a matching benefit. Writing straight to element.textContent or classList also makes it obvious, line by line, exactly which DOM writes happen and when, with nothing running through a compiler first.

Which architecture fits a given project?

An interface with many interdependent views and a team that will keep extending it benefits from Vue's component boundaries and automatic dependency tracking as the state grows. A small, self-contained piece of a page, or one embedded inside a system that already dictates its own architecture, is usually easier to reason about with direct, explicit DOM code than with a compiled component layer on top.