if you plug one side, and vent the other to PCV, then you will have reduced crankcase pressure. This will help the rings to seal, help the front seal to seal, reduce oil past the valves, minimize air flow into the carb ( thru the PCV ), and any oil vapors or other crap will get burned.

However, if you vent the one side, then you will have dramatically increased airflow thru the carb ( a lean condition you will have to correct for ) dirt and crap flowing into the engine ( need to have a filter element breather ) and you are now venting all that crap into the atmoshpere which would otherwise burn.
so in your opinion is it better to plug one side or put a breather on it?