Both are open source and in my opinion can fill about 80% of dashboards and ad hoc analysis for a small to medium company. The other 20 % your company must be rich enough to buy Tableau or rich enough to build its own solution.
Tableau is awesome, but I believe that most of its features are not used soo often. A simpler tool can provide almost the same or more value than Tableau in some cases. Well, a tool that you don't need to pay expensive licenses for each user makes it more democratic, everyone on the organization can visualize and create new analysis.
I totally agree we need something cheap and simple, but it must have some level of "functional" calculations a la excel. Now if users were exposed a pandas dataframe in Superset or Redash or other, that would be extremely cool and would for some cases be much better than Tableau.
Can Metabase do this? I struggled to get a This Year vs Last Year chart without messing with the underlying data.
Is there a good book on Metabase out there?
for instance, for a query like:
select day_of_year, year, count(*) from orders where year >= 2016 group by day_of_year, year
you can create a line visualization that will display the different years as different lines in about 2 or 3 clicks.
AFAIK, there is no book for Metabase. But the documentation and the project is really straightforward.