I agree with Ray. I do both, but not hydroponics for orchids.
I think it's fair to say that hydroponics, whether Flood and Drain ( Ray's ebb and flow) or spray technique is an automated, capital demanding process system.
Semi Hydro as Ray has dubbed it is a simple, manual method for growing orchids which requires little expense or understanding of control systems.
Those are my definitions, but I guess everyone could make their own and still be right.