Hi Manoj,
There is no "ArcGIS Server vs Versioning" comparison to be made.
When you view a map in ArcMap and you're accessing data from an enterprise geodatabase (which has versioned datasets), you connect to a specific version in the geodatabase. When you publish the map, either as a map service or feature service, the web service accesses the enterprise geodatabase data via the version that was specified. This is used throughout the rest of the WebGIS stack.
Versioning behavior (e.g., editing workflows) is honored and works at the enterprise geodatabase tier.
Hope this helps,