It's ActiveSync vs. Exchange Web Services (EWS) again.
ActiveSync comes with complicated licensing requirements (from Microsoft), so I chose to use EWS instead. Dealing with ActiveSync licensing is just too difficult for a guy in his bedroom.
Some companies and people who develop email apps have ActiveSync licenses (Samsung, HTC, Sony, LG... Enhanced Email, Moxier Mail, TouchDown)...
Some don't, and choose EWS instead (yours truly, MailDroid...)
Standards are great. Everyone should have his own.