Same brand, same $399, opposite trade-offs. The R5 is a full bundle at 5.5 Nm - base, ES wheel and SR-P Lite pedals - while the R12 V2 is a bare 12 Nm base. So for identical money you are choosing between a complete starter kit and a much stronger base you build around yourself.
If you own nothing, the R5 gets you driving on day one and is the better value as a package. If you already have a wheel and pedals, the R12 V2 is the smarter buy - more than double the torque for the same price, and you pick your own rim. Both sit on the same MOZA ladder, so neither is a dead end.