Interior quality, in-built technology and refinement will be better on the imported Commodore, but it won't be RWD, so it's likely to not handle as well, plus you won't be able to get a V6 or V8. It also won't be a conventional sedan body style, but rather a 4 door Coupe/Notchback style. Prices will be higher too. Gone will be the days of the $40k SV6 Black edition, etc.
However, it's likely that Diesel and AWD will be offered (probably not together) and the car will feature things like radar cruise control, adaptive LED headlights, adapative suspension, 9 speed auto, ventilated front seats, lane keep assist, autonomous braking, apple carplay and Android Auto.