I don't have the 900, but I own a 505 and 600. The 505 has a much better display than the 600 due to lack of touch. But still, the 600 does all the tricks I need and glare or contrast is no issue for me. It's been said 1000 times (maybe more) that there's no wrong or right here. It depends what you need and what you expect from your reader. In my case, the 600 is perfect. The 900 probably would be, too, but I cannot get one here in a store. It's only sold via internet which I don't like.
So everyone go out and get the reader he needs. Maybe it's a 600, maybe a 300, maybe an Irex or a kindle or.....