I've found a video comparing both of them in a
thread, in case you hadn't watched it already it can be of help.
As you can imagine, I can only speak from the PB360 view.
The big buttons are stiff, which is a bit cumbersome, and probably loud, though the only moment when I can imagine that makes trouble is if you read next to somebody else. However the D-Pad works smoothly, less noise.
About the ergonomics: the sensor of the PB360 works just fine. You can read with both hands very smoothly, up to the point that I usually invert the device and use the left hand though I'm right-handed: as it leaves the D-Pad in the left side, I can concentrate better on reading text from left to right. Though of course that's a personal thing.
If you don't like the flash while turning pages, there is an enhanced software version for the HTML reader (FBReader) which allows you to deactivate it (it's been very nice for me, as I really dislike the flash). Lastly, it has never hung for me, up to date (1 month).
About the site, I've been poking some minutes with it. The content itself displays nicely, however there is content I can't get to see (random suttas, or contact information, for example). However, as it is the first HTML file I open with the reader, I'm not very savvy with it.