SSAS Tabular Model or Power BI Model

Yted, to add to what BhaveshPatel said, you can import a Power BI model to SSAS, but currently it is rather an involved process to actually accomplish that. See the following blog articles:

http://biinsight.com/import-power-bi-desktop-model-ssas-tabular-2016/

http://biinsight.com/connect-to-power-bi-desktop-model-from-excel-and-ssms/

It is currently relatively complex to get the data imported and then refresh is a whole other ball of wax. I really could not recommend it currently as a production solution.

There is an Idea out there to make this more streamlined:

https://ideas.powerbi.com/forums/265200-power-bi-ideas/suggestions/10882251-import-powerbi-desktop-model-into-ssas-analysis-se

I would vote for that.

As to your question, it is really a question of a few trade-offs/decisions that need to be made. With SSAS it is a much more complex setup. You are likely going to need a SQL Server database as well as SSIS packages in the mix. The reason is that SSAS data import only supports a limited number of data sources (compared to Power BI):

https://technet.microsoft.com/en-us/library/hh230968(v=sql.130).aspx

So, first issue is complexity. SSAS adds complexity and using just Power BI makes things relatively simple.

A couple of things that might rule one or the other approach out immediately:

• Too much data. If you have too much data for Power BI to handle, then you need to use SSAS and Direct Query to live query the data
• If your connection type is not supported by SSAS data source import or SSIS (that would be harder to believe) then you might be forced to use Power BI Desktop