Even though they are all FICO scores, each bureau uses a slightly different version (you can search here about it...lots of earlier posts). Also, the information on all three reports can be just slightly different (maybe an extra inquiry on one of em or something).
These are pretty close....they rarely are exactly the same across all three. For example, my current scores are EQ-708 (was 711 until a stupid CA did what should be an illegal hard inquiry the other day!!), TU - 690 and EX - 689. See, for me the EQ is actually the highest, even though basically they are all reporting the same information.
Also, make sure your util paydown is showing on all three reports....each of them is famous for not getting info updated at times...for me right now EQ is the slowest!