The other (AllData) uses factory schematics and data straight from the OEMs, with diagrams broken down into sub-systems and sub-sub-systems for really slick pinpoint testing. One of them (Mitchell) creates their own wiring diagrams in a format that allows the user to custom tailor and highlight just the colored circuits he needs to address, and provides proprietory blow-by-blow procedures for most repairs, like Haynes.
That's the beauty of the two mainstream services I listed above.
