I bought the Pioneer a few weeks ago from Best Buy (got them to price match Costco) but have been disappointed with it. I picked up an open-box Onkyo from Frys yesterday for just under $600 tax included, making it slightly cheaper than the Pioneer. I will be returning the Pioneer later this week.
My main reason for getting rid of the Pioneer: You can't set different crossover frequencies for each speaker. I have two Aperion Verus Grand towers for mains and a Verus Grand Center, and then two tiny satellite Polk RM6750 that came with the house for surrounds. With the Pioneer, I have to set all five speakers to crossover at 100 Hz and pass the low frequencies over to my two Klipsch RW-12d's. With the Onkyo, the suggested settings when running Audyssey quick start (haven't had time to run MultEQ XT32 yet) is 40Hz for the mains and 120Hz for the satellites. So I am losing out on much of the advantage of having floor standing mains with the Pioneer as I have to run them way above 80Hz to accomodate the surrounds.
I am running an external amp Emotiva XPA-3 to power my front stage, so pre-outs were a must for any receiver (and the quality of the receiver's amps are therefore less important to me) . I also wanted a receiver with network control and a good Android remote app. Both of these receivers have pre-outs and networking features.
I like the on-screen display of the Onkyo much more than the Pioneer. I get visual feedback of the exact volume level with the Onkyo, whereas the Pioneer only told me that volume was being changed and I had to look at the front plate of the receiver to get feedback on the exact level. This was a huge disadvantage this past weekend when I was hosting a party and someone was sitting between me and the receiver and I had to contort myself just to see what the volume was set at. The OSD of the Onkyo menu also overlays over whatever source is playing, whereas the Pioneer's OSD takes up the fullscreen. The Onkyo app also seems snappier and starts up faster without the constant connection error I would get from the Pioneer. And the Onkyo app allows me to control volume with my phone's hardware buttons, which is important because the software volume control on the Onkyo app is terrible.
The additional bluetooth card for the Onkyo is half the price of the Pioneer ($50 vs. $100), but I may not even need this as the Onkyo app already allows me to play music files off of my phone over wifi to the receiver without having to set anything up. Now to figure out if there is an easy way to stream Google Play from my phone...