I can easily say that I was ripping on Rivers for his previous two seasons. His turnovers were Geno-esque... but wow... he has been very impressive this season. I hate that, because he is not a Chief/49er nor does he strike me as a classy player.
Would I take him over Alex right now? No. Simply on team consistency/familiarity alone. That, and I still don't think Rivers offers more than Smith does. If Rivers really is more accurate or field aware? I expect that to be far more even as KC progresses... plus, Alex has far more mobility.