What is the difference between field mappings and the data wizard?

Both features can send data from Salesforce to Mailchimp. 

The data wizard has many advantages over the Salesforce to Mailchimp field mappings, however:

1. It works with any Salesforce object or email field.
2. It is run by a single user on a schedule.
3. It runs as scheduled Apex, which is efficient and less likely to conflict with other automation or apps.

Field mappings can only be used when:

1. You add a person to an audience via our Contact or Lead component. 
2. You edit a Salesforce contact or lead that is already on an audience. Changes to mapped fields will be instantly updated in Mailchimp.

But since these Field Mappings use triggers, it requires any user who might do one of above to have one of our permission sets. It is also possible for a trigger to be conflicted with.

Field mappings also offer a sync from Mailchimp to Salesforce. These mappings are used only during the primary sync. See Field Mappings for more information.