on my droid pro it's a huge PITA to have more than one account set up. on my old HTC it wasn't that bad. pretty awesome to do it on my ipad when i need to troubleshoot something in the data center
the HTC i had didn't do push to sub folders, only to the inbox
on iOS there is a screen with all the folders and/or accounts, on android you have to press a button to bring it up and the back button likes to kick you out of the email app. at least on my droid pro.
iOS 5 has this cool feature to display emails on my lock screen so i don't even have to unlock the phone most of the time
my droid pro doesn't have the unread count in the folder list. i think HTC does this, but i'm not sure