The single biggest difference between OBIEE and Tableau is that Tableau doesn't really have a semantic layer (the equivalent of the BMM layer in OBIEE). With Tableau, you have to have your data pretty well manicured in order to work effectively. While there is a lot of basic overlap in functionality, I think the two can and should co-exist in any organization.
Tableau Benefits Over OBIEE
- Quick and rapid development of reports and dashboards. Easy enough for non technical people to figure out with little to no training. Many companies will actually use Tableau for prototyping and then building the enterprise wide reports in something like OBIEE.
- Works as a great desktop reporting tool.
- Has an excellent recommendation tool for which type of visual analysis to use based on selected data.
- Great API documentation (new in v8).
- Most reports look quite good out of the box.
- Almost true WYSIWIG.
- Positioning of dashboard objects much more flexible.
- Very easy (like, click a button easy) to do advanced analysis like Pareto, linear regression, and trending.
- Fantastic free on demand training and extremely vibrant user community.
- Maps are insanely easy to use with lots of cool functionality.
OBIEE Benefits Over Tableau
- More advanced dashboarding capabilities such as conditional guided navigation. Also much better at managing tons of dashboards.
- Stronger enterprise level security and user management.
- Some charts easier to make on OBIEE (such as a funnel).
- Shared reporting objects like filters
- Better at federating data (connecting to multiple sources) than Tableau. Tableau can do it and is OK at it, but OBIEE is the best of all reporting tools at it.
- The best functioning KPI/scorecard reports. This is an area where OBIEErocks the competition.
- Great integration to other Oracle products. IE, can interface directly with Fusion/EBS/Forms.
- Has multi-user development support and better environment management/migration. To be fair, you don't really need multiple environments for Tableau or multiple users working on the same reports.
- Ad-Hoc reports can be created through the web interface by any user you grant access to. That user, however, is limited to what you have defined in your semantic layer. Tableau requires their client to do ad-hoc. However, the user can then do any kind of logical calculations or other data manipulation they wish.
- Can cache queries. Works very well and write very efficient SQL when directly querying databases. Tableau has a proprietary data format that basically works as a cube, which can slow down very quickly on large data sets. It also is is pretty lackluster at performing direct queries in the database.
While Tableau continues to add features very quickly, I still argue it isn't up to the task of a true enterprise wide reporting platform. I think it is still best served for departmental use in the hands of a data analyst.
On the flip side, OBIEE requires a lot more effort to create even basic visualizations and usually requires a full development team.
There are trade-offs to both. And honestly, I don't think there are any use cases where the choice would be between choosing OBIEE and Tableau. I think that they actually complement each other as part of a larger analytics strategy.