Welcome to the forum, Warren!
You might like to check out my review of the Onkyo TX-NR626 that I posted on this forum, linked
here. It might be a good starting point to help you consider what your "needs" are, and what might best serve them. They might both fit your needs, or perhaps neither will. Power-wise, they are very similar.
The biggest difference that I can recall between those two receivers is the auto calibration systems. Pioneer uses MCACC, and Onkyo uses Audyssey. For a single listening position, I'd call them a wash. If you have multiple distinct listening positions (like I do), then MCACC is the better choice because it can store up to six different configurations, whereas Audyssey can only store one.