Well, sifu....that depends on the quality of the join. Jap jacksons tend to be pretty good though wood:wood interference fit on the vast majority. I have a DX1 that I've clocked out-sustaining an SG standard (measured note decay @ 12 fret, D string - SG, 5s to the knee of the curve (didnt think at the time to go for a set proportional reduction :(), jackson 8s).
Korean jacksons are another story! Avoid!
Those guitars will be made with the same batches of woods and assembled in the same machines. I wouldnt worry too much - the main variables are the pickups and the particular bits of wood that ended up in the guitar. You have as good a chance of a good instrument with the cheaper one, IMO (the pickups being irrelevent, since youre gonna change them)