Is Airplay all that Important? I guess If you have apple products then I guess yes. I don't own their stuff so...I'd go for the Onkyo you won't regret it.
I'm still PC for desktop & laptop, but I have kind of defected to Apple for mobile.
The iPad is just too cool to ignore. My workplace uses iOS mobile exclusively and PC for desktop exclusively.
AirPlay is so cool. You can stream music, video, photos from your iOS devices directly to your Denon & TV. So cool.
So to me (& millions of people) AirPlay is very desirable. I bought the $95 Apple TV just to get AirPlay added to my Denon AVP-A1. It was kind of like paying for a hardware update. Netflix streaming on the Apple TV is a bonus.
I predict that Denon will add the entire Apple TV (AirPlay, Netflix, Vudu, YouTube, etc) as the next step on their future AVRs.