From a support standpoint I prefer the built in EAS on all devices. There have only been two complaints from my users.
First is the lack of flagged message support. Sure you can flag a message and unflag and spot them in the message list, but to see all your flags at once was a simple two clicks on a BBerry, or a single click in Outlook. AFAIK from talking to Microsoft devs, the flag message attribute is not a "primary" flag in EAS and therefor cannot be sorted/grouped by on an EAS device. The solution is to create a #Flags subfolder of the inbox, set it as an additional push folder on the phone and just move messages in and out of there instead of using the flag attribute.
The second is the lack of full message data push. Headers are pushed, but until you open a message it's full content is not downloaded from the server. In poor service areas that can take 20-30 seconds to open a message, where as on the BBerry it was instant.
Not sure if Good or Moxier takes care of either issue, but from my experience the flags and push content are dependent on the server, so no dice.
Do either Good or Moxier integrate with the built in contact and calendar apps on the phone? If a user loses their phone the contact data could contain SSNs, account numbers and all sorts of sensitive info. If that data isn't wiped when the app is wiped then it defeats my purpose for having remote wipe in the first place.