Usability 
Curata Reader has what I think is the most attractive visual design of the five readers. I like that it displays items in expanded form rather than as headlines or excepts that you have to click to expand. However it only displays the 20 newest items with no way to see more.
Unlike most readers Curata doesn't keep of what you have read and can't show you only unread items. That might bother some users but it's not a big deal to me as I like to read feed items chronologically from the newest to the oldest. When I find myself re-reading something I've seen before I know I'm done.
Curata Reader has good social features. You can give flag items for latter reading, give them a thumbs up or down and share them on Twitter, Facebook or by email. Curata Reader worked in all tested browsers.