Personally I would prefer Pioneer over Onkyo only because Onkyo has terrible customer support and kind of a bad rep in terms of heat/ reliability.
But in terms of measurements (Power, SNR, XTalk, THD) & SQ, I think Onkyo is top notch.
I just worry about my luck running out on Onkyo.
If reliability/ heat history is not a factor, I would pick Onkyo almost every time.