I have not compared the sound or picture on the Sony BDP-370 to the Pioneer BDP-320.
I have compared the Sony BDP-363, as well as the Sony Fat Ps3 to the Pioneer BDP-320 & the Pioneer beats them hands down on both picture & sound quality.
The Sony players i have give good audio but are not as musical as the Pioneer, they tend to err on the darker side on picture giving good blacks, but still not quite as crisp in picture quality.
I would recommend you go & see both players in action before making your choice, using the same TV so you at least have a good comparison.
Regards .. Paul.