Nice Blog post by Andrew Crouse from Piraeus consulting
Read full Blog Post:
Or just read the sumary Bottom Line
PowerBI is best used for simple data visualizations or for Scorecards and Dashboards that will not change significantly over time. PowerBI, and the Q/A feature specifically, can be very valuable for users who are not interested in diving into data sets, but who are looking for specific analytics, quickly. Another benefit to PowerBI is the value add of Microsoft Suite in the purchase, making it a great value for businesses working with a smaller budget.
Tableau is a much faster and more flexible tool that works best for deeper analytics and enterprise dashboard solutions. The flexibility available for creating a wide variety of dashboards makes Tableau the optimal choice for business that need quick results from reporting and analysis. Tableau also offers customizable geo-mapping, background images and polygon maps for visualizing unordinary data models. Tableau would be most useful to analysts and organizations that require fast adaptation to changes in their business, and have multiple users who need constant access to this data.
Off course, the best BI work will be done by professionals who utilize PowerBI and Tableau in conjunction with one another, allowing each to lend its particular strengths to the specific needs of each challenge.