- fairlogger/Logger.h: the generic component provided by fair.
- Framework/Logger.h: wraps the above and provides some O2 specific helpers which were requested e.g. by the analysis community.
- QualityControl/QcInfoLogger.h: I’ve no idea, I assume something similar to the above. @bvonhall might want to comment on that.
If you are in O2, please use Framework/Logger.h.