I did the SD thing for awhile but health care became an issue quickly when the changes made service unavailable outside of SD.
We went to Escapees in TX and got everything done without issue. They both do a good job with mail forwarding but Escapees seems to be more responsive when we want information about whether a particular piece of mail has arrived.
If you are happy with SD I don't see any reason to change services but the Escapees group is much larger and has actually gotten involved with legal issues determental to RVers and had them resolved. They are much, much more than a mailing service.