The Pioneer will have the most power with 5 or 7 channels driven and is 4 ohm certified, if either of that is of value to you. They differ in their automatic room correction software. Pioneer's MCACC seems to garner praise for its customization options and overall SQ.
I don't here too much about Yamaha's YPAO.
The Marantz has Audessey which on this forum is the favorite.
That said, if you like the Yamaha then get the Yamaha. Other than the minor "benefits" of the Pioneer the AVRs are pretty much the same in overall function.
I would just get the one that you like best.
Klipsch RF-62II, RC-500, RS-400, SVS PC12+,
Def Tech SC8000
Harman Kardon AVR 1600
PS3, Apple TV, Sharp 70" Qattron