I use both Metabase and Redash in the company that I work for. Both are really great tools and can replace (at least in part) expensive BI tools.

I'm using both not because they are complementary, but at this moment they have a distinct feature set and no one has all the features that I want/need.

Btw, congrats for the Mozilla award, really well deserved! https://blog.mozilla.org/blog/2016/10/03/moss-supports-four-...