If I go for the 1612, it'll be because I'm on a budget, this is my very first home theater setup, the Audyssey room correction feature comes obscenely highly recommended, and I really have no need for Airplay/networking/anything more than 5.1/component video upconversion/etc. that the Pioneer offers over the Denon. They're great features, to be sure, but a $70 difference (after tax) between them matters to me right now. The Pioneer does have a two-year warranty, though, and they just might be able to power my Paradigm Mini Monitors a little better than the Denon would.
On the other hand, I'm a tiny bit bitter because I didn't start receiver shopping until *just* after the Denon xx12 models stopped having ridiculous discounts in various stores' clearance sections. 1612s were going for $100, 1712s for $150, 1912s for $200, etc.