- Site templates are created based on an existing site definitions. A site need to be created with all the brandings, changes everything required before saving the site as a template (.STP).
- Site templates are stored in Content database, which means little hit on the performance and also one time deployment to the data based in a server farm.
- Site templates can be created by anyone who has owner privileges on the site. No administrative privileges are required for deployment.
- Site templates are much easier to create than site definitions but leaves less granular customization than site definitions.
- Site templates can be seen in "Site Templates" section in sites's galleries in Site Settings
- Site templates cannot work across web applications.
In short, though site templates give us numerous advantages over site definitions, site definitions give us more control over the content, and are file system based (hence performance) and further modifications to the site definition are recommended using Feture stapling approch.