I don't think I'll be much help since I like to travel with both.

My Sony 505 is smaller and lighter and there is no start up wait time when I want to read.
I have the netbook for everything else, but it is heavier and more awkward to hold onto for reading. When I have time to wait for it to boot up, it is nice to be able to go out and check my email or surf the web and to be able to back up my photos every night.
For practical reading, the Reader is (in my opinion) the better choice! There are too many other distractions available on a netbook for me to use it to read a book, I think. However, I prefer to have the flexibility of both gadgets with me if possible.