From my understanding both have the same root but different direction.
Dremio is not cover full Apache Drill functionality and probably shouldn’t.
Personally I use both for different purposes.
Drill has an nice idea as schema on the fly.
Query with filepaths and mask
It has some kind of API to create UDF, new data sources.
Dremio - all the things from prev post make it very powerful but it has to discover schema first.