I'm thinking of getting the HTC HD2 because of its 4.3" screen but at the same time I'm thinking of getting an Android instead of Windows Mobile...so whats the biggest Android screen from HTC?
It isn't out yet but if you live in US,you can get the US version(with Sprint contract) http/www.gsmarena.com/htc_evo_4g-3427.php
Aside from their display in which Desire HD uses SLCD and Evo4G uses LCD and the battery life(4G has a better one), there aren't any other differences.
http/now.sprint.com/firsts/evo4g/
Well the OP asked about a HTC device,therefore i didn't mention DroidX but yes you are right,it also has the biggest screen in Android devices currently.