If an advertiser chooses the association model, their MCA is linked to the CSS partner relatively easily. The setting of the advertiser can remain unchanged in this case, the relocation effort is very low. An email from the CSS partner to Google is enough to request the changeover. If only one sub-account is converted from an MCA, the same dangers of loss of access rights apply as with a full switch.
The advantages of the full switch method just mentioned (full access to and insight into the product data by the CSS partner) do not have an immediate effect here. However, the CSS partner can be given access to the customer account or data feed via corresponding user invitations.
Full switch and association hardly differ in handling and cooperation. It is more a question of trust, control and flexibility whether an advertiser moves his entire account to the MCC of the CSS partner or is connected via the association.