As with any valuelss ability, the AI chooses which PDC to use by tech reqs and component level, not by damage or any relevant criteria. Add some dummy tech reqs to the one you want the AI to use (multiple entries for the techs it already requires are perfect), and boost its roman numeral values by 1. This will cause the AI to use it over others.
If you want more detailed info, we are in the process of writing a formal guide to this very topic over on ModWorks:
*link*