I don't know if
Dreams Unlimited gives any perks for booking with them but the biggest perk of using a Disney specialized TA is their wonderful service which is free of charge to you. They know the moment Disney promos are released, and on the phone the moment lines are open, getting you the best deal. Making payments is easy, just a quick email to the TA does it. Same with any questions, requests, or help with planning.
Also, if something goes wrong on arrival, and not getting help there, a quick text or call to your TA does wonders to straighten things out.
I remember a post about that awhile ago. Person had some problem, can't remember what now. CM or manager wasn't helping. She phoned her TA, who made some calls and had things straightened out in minutes.