[grayrest]

Solid works differently in that the output is implemented as a side effect of a subscription to a piece of state. Simplified, think of a signal as an event emitter and a variable with a getter and a setter. Using the getter adds its downstream effects–most notably adding/modifying DOM nodes–as an event listener. Using the setter updates the state and triggers the event listeners.

Most other frameworks here (all? not sure about Vue) will invalidate and rebuild an entire component subtree if a piece of state in them changes. The solid runtime doesn't care about components so changing a piece of state high in a subtree will only update the piece of the DOM directly depending on that state and not any nodes that were authored as sub-components.