Sometimes the record the DJ scratches is relevant to the song - it may be part of the hook or whatever.
In other cases, such as this example, the record being scratched doesn’t seem to play a role in the song, and the DJ just need a record to scratch. In a case like that, is there a preferred type of record - like a classical or blues recording - that produces the best scratch?
It really depends on the DJ. Some prefer real records, some don’t. But the classic records that are used for the scratch sounds your referring to are actually called Scratch Records, Break Records, and a few other less common names. Here’s an example:
http://www.turntablelab.com/collections/scratch-break-records-date
And a related article from a well known underground DJ (member of the group Dilated Peoples): http://www.turntablelab.com/collections/scratch-break-records-date