Why Should Medicare Medicaid Dual Eligibles Join a MAPD?

I am in AZ and I have met a couple people lately that were on AHCCCS (AZ's Medicaid program) before they become eligible for Medicare. They have become so comfortable with Medicaid that they are hesitant to consider MAPDs for dual eligibles. Other than benefits such as dental, vision and OTC stuff that are offered by MAPDs for the duals, are there any other reason why these people should consider signing up for a dual program?

TIA.

Source of insurance-forums.net