Power BI Report Server versus Power BI Service: Pros and cons
The differences between Power BI Service and Power BI Report Server are well documented in the Planning a Power BI Enterprise Deployment whitepaper and the online documentation. The whitepaper by Chris Webb and Melissa Coates also includes a comparison between Power BI Service and Power BI Report Server (Jun 2017 version). Because this is a lot of information, I've summarized the most important topics.
Power BI Report Server – two options
Power BI Report Server is the Power BI on-premises alternative to the cloud-based Power BI Service. There are two ways of acquiring Power BI Report Server: 1) Purchase a Power BI Premium Subscription or 2) by making use of your SQL Server Enterprise Software Assurance license.
Limitations of Power BI Report Server - in general
Availability of new features
Power BI Report Server comes with a Power BI Desktop version optimized for Report Server. The release schedule of this version is approximately quarterly instead of the regular monthly Power BI desktop release. This means you will not be able to use new / preview features. In addition – at this moment - it’s not possible to use some regular Power BI features, such as R integration and ArcGIS maps. Features released in the Power BI service (such as dashboards and apps) are also not (yet) available in Power BI Report Server.
Limitations of Power BI Report Server – Software Assurance version
Migration to the Power BI Report Server is a one-way, irreversible migration
The Software Assurance version allows you to transform your current SQL Server Report Server to a Power BI Report Server. This is a one-way, irreversible migration.
Why choose Power BI Report Server over Power BI Service?
The biggest reason would be if you have a strict security policy that does not allow you to move to the cloud. Power BI Report Server gives you the experience of Power BI on-premises.
If you already invested in a Power BI Premium subscription or an SQL Server Enterprise SA license you are allowed to use the Power BI Report Server without any additional licenses. Only content creators will need a Pro license. In combination with the security argument this could be a reason to implement Power BI Report Server, without a big additional investment.