One is Aluminium the other is an Aluminium alloy similar to Dural, much more robust and much less likely to go out of true if knocked.
Also the quality of the bearings on the Okuma are to a very much higher spec and the machining is much more precise, you will notice this if you remove the bearings from the Okuma, they slip out of the housing and back in again, the fit is tight and precise.
The Okuma has ready spare parts availability and parts are easily interchangeable with out the need of any engineering skill or specialist tooling.
The copy looks good and is of a very similar design……AND that is about as far as the similarity goes.