The way I understand it...
The robots protocols are sort-of ad hoc and they have no teeth. They work entirely on a good faith basis. Whether a particular bot reads one, both, or neither depends upon the bot. Likewise, with whether a bot prioritizes one over the other. Its not like, for example, the
.htaccess protocols that are enforced by the Apache web server. To defeat
.htaccess, you have to defeat Apache or at least a small part of it. Robots instructions just sit in a file and the bot reads them and obeys them, or not, depending upon the bot. And something to think about, you can't secure information with robots directives, but you can reveal away information with them.
I don't think there is a good answer to your question.