Just to pipe in..... The Aztek PP is a great reader, I wouldn't say it loses hands down. The big buttons on the 360 i would find too Noisy from what I hear. The PP has a great scroll wheel and has a form factor just as good as the 360..
You should also consider the Bookeen Opus.. I have used that for a day and found it to be a great device as well.
All in all all the 5 inch devices are good machines....