Doubt between imagepress 600,650 and 710 used

Hi everyone
After years with xerox I decided to try a Canon by buying a used one. The dealers I asked offered me a 600, 650 and 710. However, they recommended the 600 since it has very few copies and they claim that all these machines are practically identical.
It is true?
He says that only the speed and very small things change, but that the print quality is the same for all of them.
Can you confirm that this is really the case?
What real difference is there between the 3 printers?
Thank you all!