It will be a preference consideration I imagine.. I started with the HD-600, went to the 580, then the 650...well you better be ready to drive the 600/650 with a great amp else they will not scale up in terms of general operability and performance in dynamics. I personally prefer the 580's signature in sound to the 600/650 and any other non-electrostatic Senn phone..but that is me..
I used to own them all then sold them, the only one bought again was the HD-580..replaced the grilles, contacts/sprins, cable to Cardas, and perf'd caprings and I love them. They pair easily with my vintage receivers and do well from tubes too.. They are not as amp reliant as the 600/650-something to consider.
The 580/600/650 all scale up with an improved source too, fyi,
hope this helps