You can use both for different jobs
Apple Health gathers health information and gives you controls over its sources and app access. EveryBand can read supported Health records, add its own independent interpretation, and optionally export permitted records from supported straps. You can keep Health as your shared record while choosing whether EveryBand adds useful context.
Health is more than a database. Apple's health features include trends, sleep-related insights and device-specific health experiences. EveryBand does not claim that Apple lacks insights or that another score automatically improves the information you already have.