I think it's fair enough to describe the Crawler as a "more aggressive Mule": the Crawlers are hotter, and have some extra midrange that helps them cut through the mix.
Technically, I think the Abraxas is a hotter Mule, in the sense that it's tonal characteristics are very much the Mule's, but in a hotter pickup. The Crawler is very similar to the Abraxas in some ways, but that extra midrange grunt is what might let us describe is as "more aggressive".
At least, those are my understandings! :)