9500 v 9510: 10 series has feeder house dust system, shoe adjustment upgrades, 8.1 L motor compared to 7.6 in 9500, more cleaning fan speed in a 10 series and different side shield system are off the top of my head.
9600 is a bigger machine: 11" wider cylinder, 5 walkers instead of 4 and a later 9600 will have a 7.6 rated at 15-20 hp over the 9510's 8.1 motor.