Hello,
They meant quite the same, but they have slight difference-
For EWS candidates, A state government is authorized to extend the income limit further for candidates seeking reservation under EWS category in the state-owned colleges and state government's jobs.

For EBC candidates, EBC Certificate can be used for Scholarship in Education and reservation in Employment under Govt. it can be a class certificate, is issued to those who fall below the poverty line.

Hope this helps!