It doesn't matter. Once a solution is deployed, the timer job will propagate the changes to all other servers.
That is the reason for packaging everything as a solution.
One the other hand, people tend to make direct changes to server (by editing files etc.) those changes will never get propagated.
Major steps to farm solution installation:
- Adding: A solution package is added by a farm administrator to the farm's solution store, which is in the farm's configuration database. This is done either with the SharePoint Management Shell (or with the object model). It cannot be done in Central Administration.
- Deploying: The solution package is unpacked, and its elements are copied to their appropriate places.
- Feature Activating: Features must be activated before they can be used, so activating becomes a third step of installation for solutions that contain Features. Features can contain content types, controls, custom actions, custom fields, files, workflows, list instances, list templates, event receivers, and document converters; although some of these cannot be included in certain scopes.
The deployment step for a farm solution creates a timer job. This timer job is used by the timer service on each web server in the server farm. The timer job also uses the SharePoint Foundation Administrative web service to access appropriate privileges to deploy solution files to each computer, so both services must be running on all servers for the deployment to succeed.
Finally, farm solution Features are registered, and schema and definition files are committed to the configuration store.
Farm administrators can choose to deploy a solution on only some web applications in the farm.