Tableau offers a richer end-user customization interface. Power BI offers custom visuals, but these are definitely developer-only at this point. The behavior you get from the baked in pieces is more rigidly defined than that from Tableau (monthly releases address these things one item at a time).
Out of the box mapping is miles better in Tableau.
Overall Tableau is more fully-featured than Power BI. Tableau aims to be a complete BI presentation layer. Power BI is positioned as the self-service and personalized consumption component as a part of a larger BI presentation layer. Microsoft would prefer that the entirety of the BI stack be made up of their technologies, but Power BI can consume other data sources, and its reports can be embedded in other apps, so it fits into other technologies as well.
We could go feature-by-feature and Tableau would win the majority of presentation sophistication bullets (more fine-grained control of display, filtering, interactions - richer collection of built-in visualizations).
The differentiator for Power BI is more on the self-service end. Personalized dashboards (dashboard and report are two distinct concepts in Power BI) can be trivially created from published reports. Customized reports can easily be extended from published reports and datasets. There's a strong collaboration framework based on Office 365 groups and with lessons learned from SharePoint. There is also a pretty seamless upgrade path. Power Pivot models can currently be promoted to SSAS, and the expectation is for the same to be possible with Power BI models (all the same backing database technology).
I hate to be so vague, but there's a lot to both products. I'd be happy to dive deeper into some specific cases if you've got questions.
Since you sound fairly familiar with both platforms, what's your take on if and how well MS is doing on making PowerBI functionally equivalent to Tableau? At the rate they are going do you expect they will reach parity in the foreseeable future?
I think the answer is yes if you buy into the Microsoft stack, which includes SSRS and SSAS being used in conjunction with Power BI. SQL 2016 is a big BI release for Microsoft.
Power BI as a standalone product is pretty brutally limited in terms of data volume (250MB compressed data model is the max that can be hosted in the cloud service), and is missing the extensibility and flexibility that comes from a tool like SSRS.
As a self contained product, Tableau will likely hold the lead for some time. As a platform, I think Microsoft is beyond Tableau - they cover far more of the BI spectrum (and well, especially with SSAS) than Tableau seems to ever intend to.
Out of the box mapping is miles better in Tableau.
Overall Tableau is more fully-featured than Power BI. Tableau aims to be a complete BI presentation layer. Power BI is positioned as the self-service and personalized consumption component as a part of a larger BI presentation layer. Microsoft would prefer that the entirety of the BI stack be made up of their technologies, but Power BI can consume other data sources, and its reports can be embedded in other apps, so it fits into other technologies as well.
We could go feature-by-feature and Tableau would win the majority of presentation sophistication bullets (more fine-grained control of display, filtering, interactions - richer collection of built-in visualizations).
The differentiator for Power BI is more on the self-service end. Personalized dashboards (dashboard and report are two distinct concepts in Power BI) can be trivially created from published reports. Customized reports can easily be extended from published reports and datasets. There's a strong collaboration framework based on Office 365 groups and with lessons learned from SharePoint. There is also a pretty seamless upgrade path. Power Pivot models can currently be promoted to SSAS, and the expectation is for the same to be possible with Power BI models (all the same backing database technology).
I hate to be so vague, but there's a lot to both products. I'd be happy to dive deeper into some specific cases if you've got questions.