There is a misleading: sysEnum enumerations are defined in the XML schema (srcSchema schema) while dbEnum are defined in the Administration>Platform>Enumerations node (xtk:enum schema).
Nota bene if you create your own enumeration:
Closed enumeration in dbEnum appears to be quite close of a sysEnum one, and for Adobe Campaigns form and webApp forms it is similar use from user point of view. And dbEnum seems easier to manage. But actually, in many cases, sysEnum are mandatory because the dbEnum string value is put as value in the schema (table) using it, while sysEnum allows int values to be inserted instead of the string displayed to select the value. So it is better optimized from SQL point of view (indexes performance, storage space, redundancy rules, string label to change). But of course usually the choice is made depending of the different user needs.