Which is better for ebook reading??? iPad or Android Tablet (both 9 inch and 7...

[BigBang1]

...inch ones)?? -Google Nexus 7
-iPad 2
-one of the 9 inch Samsung Galaxy Tabs
-any other Android Tab???

also i was always thinking why text reflow is not available in PDF formats(Adobe reader specefically, but generally i haven't seen any pdf reader that could do text reflow....)... or is there a way to activate it???