I think the verbosity is not a problem. For example if you compare

    ["string1", "string2"]

to

    <list>
        <e>string1</e>
        <e>string2</e>
    </list>

then each element has about four bytes overhead (<e> instead of " and </e> instead of ",) plus some overhead for the list itself that may be offset by putting the name of the list itself into the element.

However, the issue is that you have to write a custom parser. There is no direct mapping between your data structure and the XML file. This developer ergonomics is a big win for JSON and consequently YAML.