The motor is physically identical from the outside absolutely nothing is changed. The only difference is the driver box is gone and the power supply is no longer a big copper torroidal transformer, it is now an off the shelf switchable voltage laptop power supply. It really is not a big change. It is in response to customers requests for simplicity and an effort to help alleviate production delays as these can be made faster. From just looking at the pumps you will see no difference at all.
Yes, it will cost the same a a 6100 but the powersupply is a high wattage generic laptop power supply, the kind that you can switch the output voltage on. When it is set to 15V you will have a 6000, at 24V it is a 6100.