In theory, they should be close. Mike Jackson based his detailing on the Atlas of the Inperium, and later contributed to DGP's detailing of the sector for Travellers Digest. That formed the core of the GEnie data set by Joe Fugate, which is one of the inputs for the T5 "second survey" data which is the basis of the Mongoose data.
As I said: in theory...
(That doesn't answer "how close", though)