Hi & welcome to MR. I can't help you with comments on hanlin or Cool-er but can tell you I am very happy with my Sony.
One piece of advice though: stop looking and take the plunge. There will always be a newer, better reader coming out. If you wait for the perfect reader you'll never get one.
Also check out the
eBook library from MR. Sooooo many free books, lovingly formatted by MR members. That'll keep you reading for a while once you finally decided on one.